Green’s Dictionary of Slang

pato n.

[Sp. pato, a duck, i.e. he ‘ducks’ down for sex]

(US/P.R.) a male homosexual.

[US]P. Thomas Down These Mean Streets (1970) 102: That cat ain’t a faggot, is he? [...] Sometimes these guys are patos and if you handle them right, you get the best breaks.
[US]B. Rodgers Queens’ Vernacular.
[US]H. Gould Fort Apache, The Bronx 105: Some of the kids in the crowd began quacking, and screaming, ‘Pato, Pato,’ the Spanish word for duck, which was Puerto Rican slang for fairy.
[US]A. Rodriguez Spidertown (1994) 1: Only patos wear that shit [i.e. aftershave] Is that wha’ thum blancos need t’ score some pussy?
[US](con. 1985–90) P. Bourjois In Search of Respect 44: Who’s this little white boy who’s always calling here? Is he a pato [faggot] or something?