Linguists have been discussing "Shit Gibbon."

by Taylor Jones

Earlier this week a Pennsylvania state senator called Dumbass Trump a "fascist, loofa-faced shit-gibbon."
There was an excellent post on Strong Language, a blog about swearing, discussing what makes "shit gibbon" so arresting, so fantastic, so novel, and yet... so right (for English swearing. Whether you believe "shit gibbon" is "right" as a characterization of Dumbass Trump is a personal assessment each person must make for themselves).
The post, The Rise of the ShitGibbon can be found here. I highly recommend reading it.
Most of the post was dedicated to tracing the origins and rise of "shitgibbon." The end of the post, however, catalogues insults in the same vein:
wankpuffin, cockwomble, fucktrumpet, dickbiscuit, twatwaffle, turdweasel, bunglecunt, shitehawk
And some variants: cuntpuffin, spunkpuffin, shitpuffin; fuckwomble, twatwomble; jizztrumpet, spunktrumpet; shitbiscuit, arsebiscuits, douchebiscuit; douchewaffle, cockwaffle, fartwaffle, cuntwaffle, shitwaffle (lots of –waffles); crapweasel, fuckweasel, pissweasel, doucheweasel.
I've actually been thinking about insults like this a surprising amount. Ben Zimmer points out about "Shitgibbon" that "...Metrically speaking, these words are compounds consisting of one element with a single stressed syllable and a second disyllabic element with a trochaic pattern, i.e., stressed-unstressed. As a metrical foot in poetry, the whole stressed-stressed-unstressed pattern is known as antibacchius."
I argue that this is correct, but that (1) there's a little bit more to say about it, and (2) there are exceptions.

HOW TO MAKE A SHITGIBBON IN TWO EASY STEPS

First: I argue that the rule for making a novel insult of this type is a single syllable expletive (e.g., dick, cock, douche, cunt, slut, fart, splunk, splooge, piss, jizz, vag, fuck, etc.) plus a trochee. A trochee, as a reminder, is a word that's two syllables with stress on the first. Examples are puffin, womble, trumpet, biscuit, waffle, weasel, and of course, gibbon. Tons of words in English are trochees (have a relevant XKCD! In fact, have two! Wait, no, three! No one expects the Spanish Inquisition!). Because so many words are trochees, you'll have to pick wisely --- something like ninja might not be as humorously insulting as waffle.
That said, in principle, monosyllable expletive + trochee seems to give really good results. Behold:
fart basket, shit whistle, turd helmet, cock bucket, douche blanket, vag weasel, (I'm gonna be so much fun when I get old and have dementia. Good luck grandkids!), shit mandrill, piss gopher, jizz weevil, etc. etc. I can do this all day.
So, it's not the fact of being a gibbon per se. Various other monkeys would work: vervet, mandrill, etc. However, crucially, baboons, macaques, black howlers, and pygmy marmosets are out.
Moreover, it's not completely unlimited. Some words fit but don't make much sense as an insult: cock bookshelf, fart saucepan (which I quite like, actually), dick pension, belch welder.
Others sound like the kind of thing a child would say: fart person! poop human! turd foreman!
Yet others are too Shakespearean: fart monger! piss weasel!
Clearly some words (waffle, weasel, gibbon, pimple, bucket) are better than others (bookshelf, doctor, ninja, icebox), and some just depend on delivery (e.g., ironic twat hero, turd ruler, spunk monarch, dick duchess).

VOWELS MATTER

For a while, I've been discussing vowels in insults with fellow linguist Lauren Spradlin. Note that when we talk about vowels, we mean sounds, not letters. Don't worry about the spelling, try saying the below aloud. Spradlin has brought my attention to the importance of repeating vowels increasing the viability of a new insult of this form: crap rabbit, jizz biscuit, shit piston, spunk puffin, cock waffle, etc.
I would argue that having the right vowels actually gives you some leeway, so you can get away with following the first word with --- gasp! ---- a non-trochee! Be it an iamb (remember iambic pentameter?) as in douche-canoe, spluge caboose, or the delightfully British bunglecunt (h/t Jeff Lidz), or even more syllables: Kobey Schwayder's charming mofo-bonobo.
As you can see, this is a hot topic in the hallowed halls of the ivory tower. If the above simple formulae have motivated even one person to go out and exercise their own creativity to make a novel contribution to the English language, then I've done my job here as a linguist. Different people get into linguistics for different reasons, but this, this is what I live for. Get out there and make a difference.