Green’s Dictionary of Slang

a woman, usu. a prostitute, who is agreeable to group sex, involving vaginal (fore) and anal (aft) intercourse.

1890–1904

Farmer & Henley Sl. and Its Analogues III 56/2: Fore-and-after [...] (venery) A double-barrelled harlot. [As in the song attributed to an eminent living man of letters: ‘Sing whore, sing whore, Behind and before, Her price is a shilling – She never gets more.’.