Green’s Dictionary of Slang

1. to cheat, to swindle, to deceive; thus yentzing n.

1931		‘Und. “Lingo” Brought Up-to-Date’ L.A. Times 8 Nov. K16: YENTZ: Outsmart; defeat.
1937		J. Curtis You’re in the Racket, Too 76: There’s only one thing gets on my wick. This here yenzing party you’re staging to-night.
1938		J. Weidman I Can Get It For You Wholesale 2: Which wouldn’t mean that the coast was clear for a little fancy yentzing.
1950		Goldin et al. DAUL 243/1: Yentz. 1. To cheat. [...] ‘I got yentzed for five yards (hundred dollars).’.
1960		Taunton Courier 23 July 3/6: American slang [...] A niff-naws or a hair-bag. The moll-buzzers bullskate and the mayvins yentz.
1972		R. Barrett Lovomaniacs (1973) 327: When he finds out we yentzed him and he’s out on his ass.

2. (also yance, yence, yentize) to have sexual intercourse; thus yancing/yencing/yentizing n.

1939		‘Hotel Sl.’ in AS XIV:3 Oct. 240/2: TO YENTZ [...] to fornicate.
1941		in G. Legman Limerick (1953) 294: A fine Southern lady named Hentz / Preferred coloured boys when she’d yentz.
1952		in G. Legman Limerick (1953) 337: There was a young man of Provence / Whose bollocks were simply immense. / ‘They’re an excellent float / In a bathtub or boat, / But,’ said he, ‘what a bore when I yentz.’.
1966		R.H. Rimmer Harrad Experiment 169: They may be able to laugh at the subject of yentizing around when a Jewish comedian on the borscht circuit makes a ‘funny.’.
1977		D. Powis Signs of Crime 207: Yancing or yencing Yiddish term for sexual intercourse; although not usually used in mixed company it it not considered completely taboo.