Gnoll, Gnome, Goblin, Giant Goat

AD&D GNOLL
Gnolls are the 2HD designated enemy humanoid monsters, and have a bit more effort put into differentiating them from other Evil Humanoids™ in that they are slavers (Having 1 slave per 10 gnolls at a minimum) and notably lazy in that they do not mine as the other subterranean humanoids are known to do. In contrast to many other humanoids, gnoll leader types have maxed (or near to it) HP scores, with HP ranging from 16-22 while HD remains in the 3-4 range. The rarer above-ground gnoll settlements have hyena and hyenadons, while subterranean gnoll lairs sometimes (30%) of the time collude with Trolls. Their treasure type is a bit better than, say, orcs and goblins, though gnolls are markedly more of a threat with 2HD than weaker humanoids who tend to have similar Numbers Appearing.

While loosely hyena themed, rather than focus on, say, the matriarchal spotted hyena pack structure, Gygax instead thought it best to describe how when committing war crimes against the gnolls there are females of 50% the male warrior population and children numbering 200% the male populace, from which I think it is only fair to conclude that Gygax kicked puppies at 200% the rate he kicked dogs.

Personally, I have great nostalgia for gnolls, for they were the designated evil humanoid of the best AD&D campaign I played in back when I was like 12(best because the GM pulled no punches and killed us many a time until we played more carefully), and my best AD&D character, Brother Phillip, LN Cleric of Undeath, got his start as a prisoner rescued from a gnoll camp and designated as replacement character, the characters before him having perished trying to go full Gygaxian murder on the gnolls and being stoned to death by a horde of 'noncombatant' gnolls alongside the other player who I believe was a ranger-type. A fitting end to such murderous hubris.

I believe the current editions of D&D, while attempting to humanize traditionally spurned beings such as orcs(with mixed results), have doubled down on having Gnolls be proper capital E evil villains, being unnatural extensions of the demon-god Yeenoghu spawned from regular hyena who ate so much battle-carrion they swelled up and exploded into gnolls. That's the sort of explanation for always evil humanoids you need.

AD&D GNOME

I've never been a fan of gnomes- they seemed redundant with halflings. Like, do we really need this subset of 'tiny dudes who are like halflings and/or dwarves but more fey/scientific?' Some people are the opposite way and would do away with the halfling and keep the gnome, but I think halflings are a nice standin for human children or just little people in terms of the 'small=sneaky' aspect. Whereas a gnome is like, 'oh no, halflings and dwarves are racially incapable of being an illusionist, we need to come up with a new 'race' to fill the vital niche of 'small but also illusions.'

Anyway, that's my take on gnomes as a player race. As monsters I have little to say about them- they are very similar to the Dwarf entry, and despite the prevalence of the idea of the 'gnome illusionist' they are instead all clerics or fighters, with magic-users being rumored but not proven. I have never heard of any campaigns with impassioned battles against gnomes, or modules with fiendish gnome lairs. Of course I don't really follow such things closely so I could be mistaken.

Also they have badgers for days to guard their burrows. Regular badgers, giant badgers, and wolverines which are pretty badgerlike if you squint. I dunno.

AD&D GOBLIN
The OG disposable humanoid monster. There is surprisingly little information given to these maligned sword-fodder, no doubt due to any GM being assumed to be familiar with Lord of the Rings (no doubt where the close association with giant wolves/wargs comes from as well.) They are said to be slave-takers and fond of torture, but I'm pretty sure the Gnolls stole all the depictions of slavery and then the Drow stole all the torture.

On a largely unrelated note, I find when consuming trashy japanese isekai manga, the depiction of goblins often is a useful 'canary in the coal mine.' If goblins are killed by adventurers without question and are depicted as inhuman subsentient monsters, the manga is likely to be extra trash, but if the goblins can be communicated with and are not portrayed as sacks of XP to be beaten like pinatas, there may be hope for the manga after all.

AD&D GIANT GOAT
Exactly what you'd expect, really. They have a menacing charge attack and occasionally serve as steeds, presumably for mountain-dwellers such as dwarves. They do not, however, have any special method of knocking people down or away, which is a missed opportunity.
Not satisfied with rules for slaughtering demihuman children, Gygax includes the percentile size of juvenile goats so that kids might be slaughtered as well. Shockingly, no rules for selling giant goats kids are mentioned. Pretty sus that Gygax outlines rules to sell sapient monster kids into slavery (see Giant Beavers) but doesn't give a single shred of attention to the market for 'literal domestic animals but big.'

SUNSET REALM GNOLL
In the realm of Saresare, there was an old, old god, Ibn Haur, who had no head. So he borrows heads from others, giving them his previously-borrowed head in exchange. As the swapping went on over the aeons, there came to be many such beast-headed people in Saresare, whose children are likewise beastly, and so on. Though they have some traits of their bestial heads and indeed, some have grown more beastly over the ages, they still count as 'human' for all intents and purposes. The only animal not included are dogs (more on that later) and snakes (Yg being behind all snakey things and typically focused on getting rid of legs before swapping heads)

There are Hyena in Saresare, and so inevitably there are some Hyena-headed people. Some are bandits of the desert, other judges of the court of law, and that's all there is to it- Ibn Haur did not seem to have any plan with all the head-swapping, and even if he did, the Law rules Saresare now, not the ancient edicts of nigh-forgotten gods.

No one can stop me from using goofy old 14th century art as reference

In Yuba, there are dog-headed people known as Cynocephali. They are typically sacred priests or temple-guards of Yuban ziggurats and are often two-souled, dog and human. Due to this shared experience, they are indeed more bestial in behavior than the Saresaren variety, but really, which is likelier to be wicked- a dog, or a man? The idea that someone would be worse for having doggish qualities is laughable in Yuba, as dog is basically synonymous with 'good' there.

Outside of their home realms, either may face prejudice due to beast-men implying something rather different in other places. In the Tripartite Realm of King's Point, Queen's Coast, and Prince's Spit, such hybridization is presumed to be the work of Murulu and as such has strong connotations with the ideological enemy of the realm, so suspicion of being a spy would be high. In Vint-Savoth, the accursed Blood Moon lies dead and bleeding, spreading the scourge of beasthood, and someone with animalistic features is assumed to be turning into a contagious alien werewolf monster, so panicked beast hunts could be called and explanations disregarded.

SUNSET REALM GNOME
I've never been a fan of gnomes- they seemed redundant with halflings. Like, do we really need this subset of 'tiny dudes who are like halflings and/or dwarves but more fey/scientific?' In any case, I think a gnome in the sunset realm is less of a thing and more just a catchier and more generic term for a half-fey, often the offspring of a little person and then some manner of pixie, fairy, or other smallish alfspawn. Etymology would then imply that Sylph and Undine are similar things, so the distinction is that Sylphs are half-fey with wings, Gnomes are land-walkers, and Undine are amphibious hybrids.

A shaved goblin, an unshaven goblin, and a goblin who has recently re-discovered cosmetology

SUNSET REALM GOBLINOIDS
Goblins are the most common form of Alfspawn, and exist in a range of patterns known as 'Goblinoids.' 'Goblinoid' can be distinguished from 'humanoid' by virtue of green skin, short stature, bestial eyes, fur patterns, and teeth, and indeed, if you take certain humorous elvish lyrics at face value, humans may just be a round-eared, furless kind of goblin. To create a Goblin, the shadows of various animals, are melted together in a cauldron, and bound to serve the chef, typically an Alf Lord. They have no names or shadows, and are more akin to a golem or spellwisp than a biological creature- just made of shadows, magic and fey commandments rather than anything substantial. With no name or shadow, their identity and form are fluid but united in a general sort of idea as the animal shadows do their best to follow their anthropic programming. As for why goblins look the way they do- the answer is simple. To an Elf, a goblin is the same sort of ugly-cute as say, a pug-dog is to humans, and the classic green goblin was just the most popular model. Goblins that look more like elves or more like beasts were once quite common as well, and varied in size, shape, coloration, and everything else one might expect of a designer-being created by a race of bored aesthetes. None of them are ugly in the way a horrible burbling fungus-zombie from hell is ugly- goblin ugliness is more like comedic exaggeration for artistic effect.

However, their (admittedly weak) self-preservation rune-logic makes goblins rather keen on obtaining shadows and names and so becoming real, rather than a half-assed amalgamate of chipmunk shadows. A goblin with a name can have a individuated subjective experience of the world and true free will (this conscious thought replaces old rune-programming but will match overall motive at first), and a goblin with a shadow can have a proper biological form. Goblins with no shadows just burst into skittering animal-shadows when they are 'killed,' almost an exorcism. A goblin with both is a High Goblin, or Hob Goblin, or 'House Goblin.' Goblins either can be named in a ceremony that is a little dangerous to the goblin, or can steal a name by trickery, or can get a name naturally by picking up a nickname from their associates. Though goblins with no names can't name each other as they lack the consciousness to do so, the spontaneous organization of goblins comes about when even one gets a name, awakens to consciousness, and then ends up intentionally or otherwise naming others, who then name others, until the entire goblin gang has names and personalities. Shadows are a bit trickier, but can be stolen and traded similarly. Goblins with animal shadows end up extra-bestial, as the shadow informs the goblin's final body plan where before consistency was really more of a suggestion. Humans who lose their name, shadow, or both will become rather gobliny themselves, but have a sun-soul that keeps them more morphologically stable than a goblin is. While a goblin who is just a collection of animal shadows is more like a computer than a person, a goblin with either a name or a shadow is a living being of some kind, and Hobgoblins are basically just little green hairy people, having clawed their way up from a half-baked existence into genuine being. 

I got this from german wikipedia or something and it was titled 'kobold'

Goblins played various roles throughout the ages.
In the third age, when the spells for goblin-making were developed, they were essentially used as robots. They were servants and soldiers for those Elves did not trust humans for the role, the equivalent of using a Roomba instead of hiring a maid. Fairies, similarly created entities, were fragile and less flexible, being an anthropomorphized spell rather than an anthropomorphized collection of animal shadows, and so goblins were generalists compared to specialist Fairies.
They fought bloodless proxy wars, bursting into animal shadows when slain and causing many false superstitions to swell up among humans, as it was not clear that the shadowy hordes of goblins marching around were a symptom of elf conflict, not a separate people fighting elves, and this lingering idea of goblins being an independent force of chaos rather than the tools of elves stems from this misunderstanding. Naturally, elves can't be bothered to clear things up officially, because human societies, by their perspective, fall so rapidly and lose their libraries with such frequency that there's no point telling them anything- it would be like trying to educate fruit flies.

Confusion over goblins was therefore extremely common among humans in the 4th age, as knowledge from the 3rd age was lost in the intersolar darkness and replaced by half-remembered and entirely misunderstood tales of old, and conflict with remnant shadow-goblins protecting elven ruins, mines, forests, and with living hobgoblins who were just living their lives free of Alvish influence occurred frequently and tragically. The idea of goblins as monstrous 'sword-fodder' stems from this age, and lingering sentiment of that nature exists mainly to explain why new players drifting in to my campaign carrying expectations from other media might have those notions in-universe, so as to allow for diegetic explanation of the world rather than demanding they read oodles and oodles of deep lore.

In the 5th age, shadow-type goblins are extremely rare outside of Elfland or the Moonlands, their remnants falling to attrition from the uncounted horrors of the world or ascending to the state of true living beings. Living civilizations of goblins are mostly endemic to the Fault, where the survivors from the Riikhite crusades for the Orb in this land have prospered, reclaiming the ruins of their Alvish masters to create strongholds against the pressures of Undeath in that land once the jungles became choked with the dead. They also find work aboard the flying ships of the Gondazong, as the small frame of a goblin is good for tight engineering squeezes., alongside rat-folk hired for the same purpose, and are valued as Ratcatchers and discreet agents in other parts of the world.

Goblinoids that do not have shadows or names lean more muppet and less 'green elf' but are definitely more fairy tale and less Lord of the Rings movie depiction

Other Goblinoids
Bugbears- Just huge, hairy goblins.
Goblin King/Queens/Majesties- A term for long-lived, highly skilled goblins who typically come to rule younger, less experienced goblins.
Orcs- No longer exist, but if they did, they'd just be shaved bugbears-in-training.
Ogres- Shock/terror troop versions of goblins, with modified rune logic to avoid name-taking and instead prioritize shadow-stealing. They are the Alfspawn/Moonspawn of the Iron Moon and they are much, much closer to being true monsters than goblins.
Nilbogs- Created only during the downward spiral of the 3rd age, a Nilbog is a goblin created using the reflections of shadows, or perhaps shadows cast by darkness rather than light, or perhaps being an undead arisen from a shadow-goblin which was never truly alive, or the nightmare of a shadow-goblin which never truly had thoughts. In any case, Nilbogs are goblinoids who react oppositely to many stimuli, most notably being healed by being harmed, and vice-versa. Nilbogs are categorized as Monsters with a capital M, having no place in the waking world and bringing nothing but woe.
Humans- Though never proven, it would explain a lot
Elves- The obscure fairy tale 'Dancer in the Dark' or 'The 5th Traveler' provides an alternate origin for elves and goblins, suggesting elves are goblins who struck a deal with a thing from beyond reality to become fabulous immortal elves, in exchange for being tasked, with all of eternity as deadline, to render unto the thing the moon, the sun, and every star in the sky, and also too the black stars behind the bright stars.


SUNSET REALM GIANT GOAT
As with other giant things, anything can grow to outrageous size for a variety of whimsical reasons, so goats are no exception. Though dwarves are nearly extinct, their bred-to-be-giant goats probably outlived them to some degree, haunting the mountains of the Tripartite realm to provide Billy Goats Gruff references.