Green’s Dictionary of Slang

entrance n.

the vagina.

[UK]Whores Rhetorick 182: I remember to have heard of one honest Whore [...] Who refused the Son entrance, because the Father had already travelled that road.
[UK]Farmer & Henley Sl. and Its Analogues.
[UK]Lustful Memoirs of a Young and Passionated Girl 45: Getting a leg on either side of him, she took hold of his majesty and getting his head at the entrance to her grotto she let herself down and soon had him securely imprisoned.