Jack from Online

Princess: an effeminate and relatively youthful male homosexual or lesbian (1931-4)

Daffodil: effeminate young man (1925)

To throw a fuck into: to have sex with (1919)

Top sergeant: a masculine lesbian (1939) [‘she takes command of the girls’ privates’]

Lily: penis (1919)

Wolf: sexually aggressive man (1847); a homosexual top (1918)

Soul kiss: a deep kiss, involving putting one’s tongue into one’s partner’s mouth (1907)

Tom: a lesbian (1909); [in 'old tom'] prostitute catering to lesbians (1966)

Church mouse: a male homosexual who frequents crowded churches in order to fondle any potential sex partners. (1941)

Discover one's gender: to accept or acknowledge one’s homosexuality (1941) / Lose one's gender: To return to living as a heterosexual

Minty: a masculine lesbian (1941)

Also a lot of early 20th century vulgarity is recorded in Letter from My Father, which is a collection of letters published by a man who's dad was, in short, a major slut and human disaster who wrote about his sex life for his son. It's insane. You can find copies of it online & it's a wild fucking read (literally!) and I think a really interesting look at the life of a person who goes against our stereotypes of what people in the past were "supposed" to be like.

note for writers: these are dated to the first time they were recorded, not necessarily to their first use. I imagine for many of these, they came about naturally through spoken language before they were written down anywhere. This is especially true of more underground slang because it's probably being recorded (in ways we still have) the least. So if you wanna use a term but it's a little off date-wise, give yourself some wiggle room.

also gonna take this moment to highlight two more i found recently:

Best boy: a sweetheart, a boyfriend, a husband. (1893) [w the obvious equivalent term 'best girl']

Honeydripper or honeydrips: a sexual partner (1917)