Green’s Dictionary of Slang

callibisters n.

the vagina.

1653		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.
1890–1904		Farmer & Henley Sl. and Its Analogues.
[c.1904		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].