“black, coming from the Latin niger, by way of various Romance languages.”
I don’t now anything about the evolution of this part of language, but I’ve had a theory that TheOnlyWordThatWouldGetMeBanned actually was an alliteration of “negro” (may I say that?) - poorly spoken by poor-spoken people.
Oddly enough, "TheOnlyWordThatWouldGetMeBanned" came first. Then came the reasonable, 20th-century idea that we were entering a new era of more cosmopolitan respect for black folks. It was thought that we therefore needed a new word, inasmuch as "black" seemed stark and rude—which it is, if you happen to think there's something wrong with being black. Which the educated elites still did. They started substituting "negro" for "black," "colored" and less polite terms. To the elites, "negro" seemed more polite than "black," because it was an exotic, technical-sounding, foreign (Spanish) word . . . for black.
By the time I was a kid, southern whites had adjusted this to "nigra," which began to sound a lot like TheOnlyWordThatWouldGetMeBanned.
And of course, in due time, "Negro" became anathema to young black firebrands, because it reminded them of old black firebrands, to whom they felt superior, because the old ones went to church, and they didn't. You know the rest: Afro-American, black, African-American . . . and whatever is next. If you're in the grievance business, the term of 20 years ago always seems tinged with bigotry and surrender.