Back in 2008, Philologos of the Forward wrote about one of the best words I’ve ever seen:
Khnyok — it’s pronounced as one syllable, a feat best managed by pretending to clear your throat and blow your nose at the same time — is Yiddish. In my own enlightened Orthodox, English-speaking New York family (my father was born in Belarus, my mother in Lithuania), a khnyok was a sanctimonious religious prig, and this is what the word means to most of its users today. Rarely found in the vocabulary of American-born secular or non-Orthodox Jews, it is for the most part disparagingly used by Jews who are religiously observant themselves for the holier-than-thou super-observant. The plural of khnyok is khnyokes (two syllables, please), the adjective is khnyokish, and the past participle is farkhnyokt, which denotes someone who has become a khnyok or more khnyokish than he or she once was.
So far, the case of khnyok seems simple enough. But when one delves into the word’s origins and history, the plot thickens considerably. […]
We can now come to some tentative conclusions. As Langer was writing about the years 1913 and 1914, his use of khnyok must reflect an early meaning — and, unexpectedly, the word seems to have started out not as an anti-Hasidic slur but as a term used by some Hasidim to disparage other Hasidim who went to ascetic extremes of personal hygiene and dress to demonstrate their contempt for worldly existence. […] From there, the word left the confines of the Hasidic community and went off in different directions: Because unkemptness is associated with oafishness, it came to mean a bungler or schlimazel; because schlimazels are often doormats for others (it’s on the schlimazel, you’ll recall, that the schlemiel spills the chicken soup), it came to mean a whiner or mollycoddle, and because its original meaning of an extreme Hasid was picked up by misnagdim, or anti-Hasidic Jews, it eventually became a derogatory term both for Hasidim in general and for a religious fanatic of any stripe. Today, it survives only in the last of these meanings.
Still unanswered is the question of khnyok’s etymology. Harkavy’s suggestion of Russian khnyika does not really explain anything and needs, I think, to be discarded. If any of you has a better idea, let’s hear it.
I just wish my friend Allan were still alive, because he could have given me some great reminiscences about this word, and if he didn’t already know it, how he would have loved it!