Green’s Dictionary of Slang

1. (US, also goopher) a lout, an oaf, a clumsy fool.

1918		Taunton Courier 2 Oct. 6/2: [from N.Y. Eve. Sun] All good eggs [are] soon promoted to goopher standing. This is when they have to prove themselves gimpers .
1920		F.S. Fitzgerald This Side of Paradise in Bodley Head Scott Fitzgerald (1965) III 79: Don’t be a critical goopher or you can’t go!
1927		R. Lardner ‘Hurry Kane’ in Coll. Short Stories (1941) 91: Dave’s dope was good, but you can’t [...] prevent a bunch of ball players from kidding a goofer like Kane.
1930		J. Lait Put on the Spot 5: You don’ mean we’re gonna let them West Side goofers get away with this!
c.1943		‘Bill O. Lading’ You Chirped a Chinful!! n.p.: Goopher. Plenty wrong.
1981		D.E. Miller Bk of Jargon (list of tennis terms) 244: Goofer and goober. A loser, not only in fact and habit, but also by preference or temperament.

2. a homosexual prostitute who will take active roles in fellatio or anal intercourse.

1965		Guild Dict. Homosexual Terms 19: goofer (n.): A male who prostitutes only his penis to homosexuals, either fellators, mutual masturbators, or passive pedicants.
1972		(ref. to 1940s) B. Rodgers Queens’ Vernacular 112: Hustlers too have their sexual proclivities: a goofer (’40s) or a baggage [box-]-boy allows only his cock to be the currency of sexual sale.