Content note: by dint of the subject matter, this post is going to contain a number of offensive words.
You can learn a lot about a society by looking at what they consider to be insulting.
The basic principle is pretty simple: if you want to speak negatively about a person, you ascribe to them qualities you consider to be undesirable. Or — as a corollary — it isn’t so much the qualities as the way they’re spun; the same action might be described as courageous if you approve of it, reckless if you don’t. (I’ve always found it interesting that sangfroid is a good thing to have, but being cold-blooded is bad . . . even though those literally mean the same thing.) So when you’re trying to decide how to insult a character, the question is what the speaker considers to be bad, and how the target’s behavior can be framed in those terms.
There are patterns in how this tends to play out. One is stupidity: even in the current anti-intellectual climate of the United States, we generally agree that being stupid is not good. Because of the blurred line between this and outright mental disability, stupidity has been on the euphemism treadmill for literally centuries, as we bring in a neverending series of new, theoretically neutral terms for disability, which then become all-purpose insults. Fool, dunce, moron, cretin, imbecile, retard — the list goes on and on. “Cretin” is not derived from an ethnic insult for people from Crete, as I once saw a blog post suggest; it’s from the French chrétien, “Christian.” And not because “Christian” was an insult: on the contrary, it was used to distinguish human beings from brute animals, so calling a disabled person a Christian was supposed to remind you of your shared humanity. (Unfortunately, it didn’t work.)
Speaking of brute animals, that’s another common way to insult someone. Many languages use the qualities of animals both as praise and as condemnation, depending on the quality in question. In English, you can insult a woman (or these days, a man) by calling them a bitch, a female dog; in Spanish it’s zorra instead, i.e. a vixen, a female fox. In Japanese, chikushou or “beast” is kind of an all-purpose swear word. Being cold-blooded likens you to a reptile, which is off-putting to our mammalian biases. The Chinese zodiac may promote the admirable qualities of the pig, but in English calling someone by that name is not a compliment — and can anybody confirm or deny that this is especially true among religious groups where pork is considered unclean? I also wonder if animal-based insults are less common in cultures that occupy less dominant and distanced of a position over the natural world. Or maybe they’re more common, because those people, being intimately familiar with animal behavior, know exactly when you’re acting like the worst of them. Seeing which animals get singled out for metaphorical use, whether positive or negative, fills in a whole realm of symbolic thinking for that culture.
Going back to “bitch,” gender is an unfortunately common source of derogatory terms. When women are considered to be inferior, one of the worst things you can do to a man is to compare him to a woman. Conversely, a woman who acts too much like a man will find herself insulted on those grounds instead. “Bitch” is notably versatile in this regard: when applied to a female target, it usually means she’s being too strident, aggressive, etc, i.e. the negative version of what in a man would be considered confident and assertive behavior. But when applied to a male target, it usually implies weakness, lack of spine, and other supposedly womanish qualities. If you’re trying to depict a society without strict gender roles and their associated chauvinism, therefore, it helps to scrutinize your language for these kinds of gender-skewed idioms and scrub them out.
This rapidly slides into matters of the body, as sex-specific characteristics become synecdoche for the whole. A man you don’t like might be a dick or a prick, even though we have other aspects of our culture that valorize the male body. The female equivalents tend to carry more negative weight: pussy, cunt, etc. On the other hand, that latter word has a degree of general usage in British slang that’s unthinkable in the U.S., while the former has recently been repurposed in American politics via the “pussy hat” phenomenon and “Pussy Grabs Back.” Nobody’s yet stood up for the word “asshole,” though (despite the fact that, as the saying goes, assholes are like opinions: everybody has one. Or rather, the other way around). Until we start having conversations with sentient dung beetles, I’m pretty sure that everything associated with defecation is going to remain conceptually unclean and therefore fair game for insulting use.
Sexual behavior is a whole field of its own where this is concerned. Here gender comes right back in: a man who sleeps around might be a stud (good), but a woman who does the same is often a slut (bad). Harlot, whore, skank — again, the list goes on and on. Men more often get hit from the angle of homosexuality, which has seen a whole lot of reclamation effort in recent years, where U.S. parlance is concerned. Gay, fag/faggot, queer, fairy, and other such terms have been embraced by the LGBTQ movement, though others have fallen almost completely out of use (e.g. molly or nancy) and some are still right out (tranny for a trans person). And then there’s the product of certain kinds of sexual behavior: calling someone a bastard no longer carries the connotation of illegitimate birth, but that was its origin, and as such it used to be grounds for a duel.
And then we have the racial, religious, and national slurs, which are unfortunately endless. The euphemism treadmill has been busily turning for people of African descent in the United States; the NAACP is a prestigious organization, but using the phrase “colored people” these days is unacceptable, while “people of color” (whose meaning is broader) has been gaining currency. Lots of these terms came into use when we were at war with a certain country and then faded after the war ended, because they reflect the political tensions of the time — so the ones that are still around are a good pointer to where those tensions are alive and well. Then they serve double duty, because you can insult someone not of that group by calling them an X-lover or other such pejorative. A few of them have gained wider use: saying that someone “gypped” you is a reference to the supposed dishonesty of gypsies, the people more properly known as Romani, while “welching” or “welshing” on a bet is possibly an artifact of the perception that Welsh people were likewise dishonest, and “jewing” indicates driving a hard bargain or even cheating.
The ones that really interest me in secondary worlds, though, are the terms that are really specific to their culture. References to great traitors of the past (as “Judas” is still used sometimes today) give you a sense of history’s ongoing weight, if the reader has some context for the term. A really militarized society might use words like “civilian” as a way of sneering at people who don’t contribute enough to the war effort. In the comic book series Elfquest, the hunter-gatherer Wolfriders’ ultimate expression of condemnation is “meat to be wasted” — a person so contemptible they don’t even deserve to play a final role in the food chain. These types of things take work to invent, and more work to sell the reader on the offensiveness of the term . . . but when done right, they make a vivid contribution to the mental landscape of the setting.