A notable early pop culture usage of the word "gay" to mean "a homosexual male":

In the movie Bringing Up Baby, Cary Grant is running around frantically in Katharine Hepburn's fur-lined bathrobe. The doorbell rings and he answers it with an anxious flourish. The man beyond the door gapes at his attire, and the enraged and nervous Grant explains: "I just went gay all of a sudden!" He leaps high into the air when he speaks the word "gay", sending the fluffy robe fluttering about.