Green’s Dictionary of Slang

(US gay) a term of address used to one who is presumed to be a fellow homosexual.

1933		J. Conroy Disinherited 192: Powdered, perfumed and rouged men strolled among the benches and occasionally accosted a bum [...] They addressed one another as ‘Agnes,’ ‘Gertrude,’ or some other feminine name.
1972		B. Rodgers Queens’ Vernacular.