Green’s Dictionary of Slang

irritable, whiny.

1945		in Commentary 2: [...] it represents with perfect fairness the tone and substance of Levin’s kvetchy self-importance.
1967–8		Baker et al. CUSS 149: Kvetchy Constantly complaining and irritable.
1978		L. Kramer Faggots 69: Dare we pause a moment to tarry over the likes of kvetchy, schleppy, nasty Lester Lemish?
1994		J. O’Connor Secret World of the Irish Male (1995) 193: The group became more and more kvetchy.
2003		N. Friedman Kindred Spirits 276: I would come to those sessions most often depressed, down, blue, kvetchy, physically achy, self-doubting, unconfident.
2023		(con. 1962) J. Ellroy Enchanters 137: The U.S. dailies [...] spritzed [...] kvetchy grief.