'Gay'

They also used the term "queer" a few times in the film.
I remember my Mother telling me that back in the 40's and 50's Gay men were known as "Buggers" or "Fruits" and Gay women were known as "Fellas" and "Jacks"

I can remember hearing it as a kid circa 1953, at least.

i don't think it was used in the 30s when it was set, if so, it dates it considering it was made much later. queer would have been used more often back then i think

I don't remember exactly where, but I recall reading somewhere that "gay" (in the sense of homosexual) was used within the gay community for a few decades before it came into common usage among the wider population. If that is true (which I can't confirm right now), then it's not necessarily out of place in the context of this film.

In the 1938 movie Bringing Up Baby, Cary Grant is found dressed in a frilly bathrobe and he comments that he "went gay." Apparently, this usage already existed in the 1930s but was underground slang that many people (including the Hays Commission) weren't yet aware of. It didn't go mainstream until the 1960s.