Green’s Dictionary of Slang

(US) a confidence trickster.

1881		Trumble Man Traps of N.Y. 28: Among the numerous small swindles [...] there is none more curious than that of the flim-flammer.
1887		N.Y. Times 13 Feb. 5: He was recognized as an expert ‘flim-flammer,’ as the men who practice this swindle are known in police parlance.
1894		Boston Journal (MA) 2 May 9/7: She notified the police, but the flim-flam artist was far away [OED].
1895		Merck’s Market Report 4 451: A DRUGGIST FILIM-FLAMS A FliM-FLAMMER. The police of Brooklyn warned storekeepers to look out for three men who were working the flim-flam game.
1906		E. Hubbard Love, Life and Work 🌐 All this whirl is a carefully prepared plan, worked out by expert flim-flammers to addle the reason.
1909		I.L. Nascher Wretches of Povertyville 220: The flimflammer invariably places a one dollar bill at the bottom and a larger bill next to it, to be withdrawn when the change is returned the second time.
1922		Laker Co. Times (Hammond, IN) 27 Mar. 4/4: Flimflam artists are doleful guys.
1924		G. Henderson Keys to Crookdom 405: Flimflammer. A swindler. Flimflam worker.
1936		(ref. to 1920s) L. Duncan Over the Wall 30: It was small stuff to the big-shot flim-flam artists, but it was buying beans and bacon for us.
1949		Monteleone Criminal Sl. (rev. edn).
1958		D. Burley N.Y. Amsterdam News 22 Mar. 13: He jived through the slammer like a sidewalk flim-flammer.
1964		Salt Lake Trib. (UT) 25 May 18/6: [headline] You’re an Old taradiddler and a Flimflammer, Too.
1979		‘Iceberg Slim’ Airtight Willie and Me 16: A friendly white man on the train warned me about flim-flambers.
1989		J. Morton Lowspeak 60: Flim-flam man – con-man.
1990		S. Morgan Homeboy 13: Pennyweight ponces and flyweight flimflammers; diddyboppers, deadbeats and dopefiends.
1998		L. Sanders McNally’s Gamble 117: I had confidently expected Frederick Clemens to reveal himself as a flimflammer peddling penny stocks and fake Fabergé eggs to gullible clients.
2005		Online Casino News 21 Nov. 🌐 [headline] Casino Flimflammer Sentenced to Seven Years in Prison.
2012		G. Pelecanos (con. 1972) What It Was 46: The burglars, car thieves, dope cutters, pickpockets and flimflam artists he knew.
2023		(con. 1962) J. Ellroy Enchanters 3489: She comported with [...] armed robbers, and flimflam men.