contrapunctum, n. — Green’s Dictionary of Slang

contrapunctum n.

[Lat. contrapunctum, lit. ‘counter-point’. The penis is the ‘point’ in this context]

the vagina.

1653		Urquhart (trans.) Gargantua and Pantagruel (1927) I Bk II 328: I see that the sine qua non, callibistris, or contrapunctums of the women of this country are cheaper than stones.
1890–1904		Farmer & Henley Sl. and Its Analogues.