yentzer, n. — Green’s Dictionary of Slang

yentzer n.

[Yid. yenzter, synon. with fucker n. (3) but lit. f. contrived euph. yents, trans. as ‘that’ or ‘the other’]

(US) a cheat, a deceiver, a liar.

1936		Mencken Amer. Lang. (4th edn) 577: He [...] borrows others from foreign languages, e.g., [...] ganov, kibitzer, kosher and yentzer from Yiddish.
1950		Goldin et al. DAUL 243/1: Yentzer. A cheat; one who defrauds his associates of their full share of loot, or turns state’s evidence when arrested, or in any other way violates the ethics of the underworld; a policeman, or any other official, or buyer of stolen goods, who does business with the members of the underworld and fails to fulfill his side of the bargain.
1970		R. Fabian Anatomy of Crime 194: Yentzer: A racketeer.
1989		J. Morton Lowspeak.