Green’s Dictionary of Slang

1. (latterly US black, also fly guy) a sophisticated, intelligent, stylish young man.

1886		Nat. Police Gaz. (NY) 26 June 6/2: ‘He is just like one of those natty, fly boys up in Wall Street’.
1895		E. Townsend Chimmie Fadden Explains 67: ’E says dat I was er pretty fly boy, an’ otter be in polytics.
1979		Funky Four + 1 ‘Rappin and Rockin the House’ 🎵 For all the fly guys, gonna hit the top.
1981		C. Hope Separate Development 193: Koos Mafeteng, a flyboy from the townships.
1985		T.R. Houser Central Sl. 22: fly boy An ‘in the mix’ man. An alluringly attractive man.
1991		B. Hamper Rivethead (1992) 174: Well-groomed fly-boys sucking on silver pens with pictures of children propped like tombstones on their desks.
1996		P. Beatty White Boy Shuffle 63: Two minutes before nine o’clock signaled the grand entrance of the fly guys and starlets.
2002		‘Touré’ Portable Promised Land (ms.) 153: We Words (My Favorite Things) [...] Threads. Dapper. Dipped. Clean. Sharp. Diva. Playa. Fly girl. Fly guy.

2. a ‘wide boy’, a spiv n.

1941		G. Kersh They Die with Their Boots Clean 37: John Johnson of Birmingham; of Brummagem, gentlemen, the breeding-ground of the Fly Boys from time immemorial.
1974		‘P.B. Yuill’ Hazell Plays Solomon (1976) 59: You’re a fly boy, Hazell [...] I suppose it’s bred into you.
1986		(con. 1920s) P. O’Farrell Tell me, Sean O’Farrell 52: The lads got off lightly and I was glad. They were taken advantage of by a fly-boy of a tinker.
1998		I. Welsh Filth 273: It’s no difficult to find your fuckin fly-boys in this city.
2000		Guardian 6 Jan. 7: A ‘flyboy’ London estate agent.
2012		C. Stella Rough Riders 26: One of your flyboy friends is selling in town. Nigger named Tyrone?