Green’s Dictionary of Slang

1. a showy but ineffective sportsman or worker.

1933		W. Winchell On Broadway 3 May [synd. col.] Add Baseball Slang. [...] ‘Fancy Dan’ — one who poses and puts on airs.
1940		J.R. Tunis Kid from Tomkinsville 77: Fancy Dans are a dime a dozen out there round short [stop]. Gabby has something else. Fight, get me?
1947		B. Schulberg Harder They Fall (1971) 245: A regular fancy Dan [...] but he’s got natural ring sense.
1973		(con. 1923) T. Loughran in Heller In This Corner (1974) 115: I always thought you were a Fancy Dan, but now you’re on your way to the title.
1983		J. Ciardi A Second Browser’s Dict. 96: Fancy Dan. [...] 2. Boxing. A fighter who boxes artfully and has fancy footwork, but who cannot deliver a powerful punch.
1998		R. Hundley You Gotta Love It Baby! 206: Hughes was a ballyhooed showman, a Fancy Dan who took all kinds of crazy shots.
2009		L. McIlvanney All the Colours 171: And here’s me, the fancy dan from Glasgow, snapping my fingers and watching him jump.

2. a flashily dressed man, a dandy.

1941		A. Lomax Mister Jelly Roll (1952) 49: Then you could observe the fancy Dans, dressed fit to kill.
1951		L.R. Morris Incredible N.Y. (1975) 35: In his leisure hours, on parade, [the Bowery Boy] looked like a fancy-Dan. He wore a tall beaver hat, an inordinately long black frock coat, loud, checked, bell-bottomed pants [etc.].
1965		Pantagraph (Bloomington, IL) 9 May 10/6: A fancy Dan or dude is a person dressed in good clothes.
1983		J. Ciardi A Second Browser’s Dict. 96: Fancy Dan. A flashy dude.
1993		A.L. Cohn From Sea to Shining Sea 278: Annie fell head over heels in love with that fancy Dan.
1998		B. Carton Beyond the Brooklyn Bridge 36: Her gentleman friend [...] was really ‘a fancy Dan, a spender, believe me,’ out to show her a ‘swellegant night on the town.’.
2002		Donald ‘Ben’ Hogan Letters to Lou – the Sequel 132: The ‘Fancy Dan’s’ from Maine, the perfect gentlemen, had better be careful with the red-eyed and rowdy animals from the decks and bilges.

3. anything showy.

1978

S. Longstreet Straw Boss (1979) 225: Those local firms are fancy dans ... they represent Ford and General Motors.