Green’s Dictionary of Slang

the vagina.

1564		Buckley ‘Oxford Libell’ in Williams (1993) II 629: Through the bridge we see ye water runne / A gulfe wth bottomles is thought.
1576		Lemnie Complexions (trans. Newton) 101v: Dissolute lecherers ... whose whole care ... is to drowne themselues in the gulph of Sensuality.
1598		Florio Worlde of Wordes n.p.: Golfo di setalia, the rugged or bristly gulfe, a woman priuities.
1605		Marston Dutch Curtezan I ii: Curtian gulfes that will never be satisfied, untill the best thing a man has be throwne into them.
1618		N. Field Amends for Ladies II i: Had I a dame whose eies did swallow youth, Whose vnchast gulph together did take in Masters, and Men, the Foot-boies and their Lords.
1635		J. Howell Familiar Letters (1737) II 15 Jan. 336: While the Husband is abroad upon the Gallies, there be others that shoot his Gulf at home.
1640		H. Mill Nights Search I 257: Strive T’avoid such gulfes, which swallow men alive.
1683		J. Oldham Advice to a Painter 338: [She is a] Damn’d Gulph of Lust.
1691		R. Ames Folly of Love 13: [Who can] sufficiently deplore, That fatal Gulph we call a Common Whore?
a.1704		N. Ward ‘The Rise and fall of Madam Coming-Sir’ in Writings (1704) 397: The little Author of my pains, at the end of one long Squeak, shot the Gulph of Venus, and made his entrance into the Wicked World.
a.1731		N. Ward Advice to an Old Lady, who has bury’d Six Husbands in Miscellaneous Works IV 9: [He is] decoy’d, To shoot that Gulph which has 3 brace destroy’d.
1765		Harris’s List of Covent Garden Ladies 79: [T]he pleasure-gulph of natured beautifully shaded with a downy brown-coloured moss.
1787		Harris’s List of Covent-Garden Ladies 30: The mature voyager to the gulf of Venus [...] stays longer in port before he pays his tribute.
1980		Maledicta IV:2 (Winter) 182: The simplest words in common use for this ‘nasty thing’ [...] are those accepting the female sexual apparatus as a simple receptacle. These include [...] gulf (hence gulf-oil).