Green’s Dictionary of Slang

a male homosexual.

1952		J. Jones From Here to Eternity (1998) 425: He is not only a pig, but he’s as queer as a fruit cake.
1963		in T.I. Rubin Sweet Daddy 40: I told Jolly, you know the nut fruit cake. I kind of slipped it to him easy that tommy is Big Sol sack’s boy.
1970		E. Tidyman Shaft 136: Some village broad named Valerie shot up a fruit-cake painter a while back.
1990		S. Morgan Homeboy 67: The fascist fruitcake gasped when he saw the handcuffs [...] So shiny.
2004		J. Ellroy ‘Jungletown Jihad’ in Destination: Morgue! (2004) 352: He humps homos. [...] The fruitcake Freddies freak.
2005		Mad mag. July 43: The Queer Cartoon Threat To Your Children [...] The sinister plot [...] to turn your child into a flaming fruitcake.