Green’s Dictionary of Slang

1. (US) a woman, a girl.

1949		Dan Burley ‘Dan Burley’s Clothesline’ 22 Oct. [synd. col.] Whether you’re to be able to court a gray Mable without the [...] nightgowners sniffing and snorting at your heels.
1952		in N.Y. Herald Trib. 29 Oct. n.p.: For a girl, just any girl, the cats now say Mabel.

2. (Aus.) a girlfriend.

1941		Argus (Melbourne) 15 Nov. (Supplement) 1/4: I have knocked out a rough glossary of Australian army slang [...] Mabel: the girl friend .
1955		N. Pulliam I Travelled a Lonely Land (1957) 235/2: Mabel – a girl friend, sometimes similar to our ‘sweetheart’ when used more or less jokingly.

3. (US gay) a black man.

1972

B. Rodgers Queens’ Vernacular 62: black man [...] [Miss] Mabel.