Green’s Dictionary of Slang

1. to inform, to inform on.

1925		Flynn’s 24 Jan. 119/1: Fink, to squeal; to inform on.
1935		D. Lamson We Who Are About to Die 106: I don’t think the guards expect you to fink.
1949		W.R. Burnett Asphalt Jungle in Four Novels (1984) 133: Where do you guys get off trying to make me fink?
1953		R. Chandler Long Good-Bye 56: Suppose you had to hire a private eye [...] Would you want one that finked on his friends?
1965		L. Bruce How to Talk Dirty 134: Felons ashamed of having finked out eagerly at their first sight of bars.
1968		T. Wolfe Electric Kool-Aid Acid Test (1969) 194: More lying, finking, framing, politicking by the constables than a body could believe.
1973		E. Bunker No Beast So Fierce 77: After vehemently denying that he’d finked on Lionel and Bulldog [...] he told of how he’d been the middle man in peddling some hot diamonds.
1980		E. Folb Runnin’ Down Some Lines 36: The highest mark of a real partner was that the person didn’t fink [...] by informing.
1987		(con. 1967) Bunch & Cole Reckoning for Kings (1989) 111: He was, however, never [...] finked on by any of the GIs to officers.
1999		Guardian Guide 15–21 May 18: A Fox rep [...] asked us to fink on anyone seen videotaping the screen.
2000		F. Kellerman Stalker (2001) 557: Trying to get information about him only to fink to her dad.
2001		OnLine Dict. of Playground Sl. 🌐 fink n.v. someone who rats on a friend or another child by passing information relating to a misdemenour of some sort to an adult [...] As verb, e.g. ‘You finked on me!!’.
2021		J. Ellroy Widespread Panic 89: ‘Fink out all the skeevy goings-on I see [...] I’ve finked to HUAC, and I’ll fink to you’.

2. to back down, to let down.

1959		W. Brown Teen-Age Mafia 38: Let him fink just once more go back on his Pachuco oath and Pico would stink a shank right into his stinking heart.
1966		Time 7 Oct. 38: When Castella Branco decreed that the next President would be elected by Congress, the opposition finked out.
1968		Current Sl. II:4 4: Fink out, v. To disappoint.
1971		E.E. Landy Underground Dict. (1972) 78: fink out on [...] Fail to do something; stand someone up; make a promise and fail to keep it.
1979		W.D. Myers The Young Landlords 121: I knew that wasn’t right, to fink out on a friend just because you were a little scared.

3. to brand as an informer.

1963

in T.I. Rubin Sweet Daddy 31: Goes to the screws, hell be finked all over the place.