Green’s Dictionary of Slang

1. a promiscuous woman.

1904		Number 1500 Life In Sing Sing 246: Bug. A trollop.
1949		Monteleone Criminal Sl. (rev. edn).

2. the vagina.

1986

S. King It (1987) 400: Beverly had overheard Greta Bowie telling Sally Mueller that the sex-act thing hurt like fire and no nice girl ever wanted to do it (‘At the end of it the man pees all over your bug’...).