Green’s Dictionary of Slang

callibisters n.

[callistris, the penis]

the vagina.

[UK]Urquhart (trans.) Gargantua and Pantagruel (1927) I Bk II 328: [note] Why callibistri (for that is the singular of callibistris) should signify a woman’s tufted honours I know not.
[UK]Farmer & Henley Sl. and Its Analogues.
[[UK]A. Crowley Snowdrops from a Curate’s Garden 22: Poor little devil! As I came, she shot off my well-oiled plenipo and was immediately split up from the fork to the shoulders by the giant callibistris of Lord R...y].