Green’s Dictionary of Slang

old hat n.

1. the vagina [‘because frequently felt’ (Grose, 1796)].

[UK]B.E. Dict. Canting Crew n.p.: Top-diver a Lover of Women. An old Top-diver, one that has Lov’d Old-hat in his time.
[UK]Levellers: A Dial. concerning Matrimony in Harleian Misc. V (1810) 451: My dear sister, be cautious in this point [...] let no old fornicator be an assessor, commissioner, or collector of your duty: he has, in his time loved a bit of old hat.
[UK]C. Walker Authentick Memoirs of Sally Salisbury 103: If the Pedantick Blockhead should come, he should only have a little bit of Old-Hat to stay his Stomach, till he got some Harlot of his own Purtanical Flock, for his Money.
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]Fielding Life of Jonathan Wild (1784) II 176: [footnote] The term Old Hat, is at present used by the vulgar in no very honourable sense.
[UK]Sterne Tristram Shandy (1996) 255: A chapter of chambermaids, green-gowns, and old hats.
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Grose Classical Dict. of the Vulgar Tongue (3rd edn) n.p.: Hat, old hat, a woman’s privities; because frequently felt.
[UK]J. Bell Jr. (ed.) Rhymes of Northern Bards 254: Each cuddles his coney or rabbit, / And pleasantly purrs with puss-cats; / Hence with husky harlots cohabit, / And handle a herdling’s old hats.
[UK]‘Jon Bee’ Dict. of the Turf, the Ring, the Chase, etc.
[UK]‘The Blowing’s Catalogue’ in Funny Songster in Spedding & Watt (eds) Bawdy Songbooks (2011) III 45: For slashing size and lip so bold, / And old hat so black with hair / It is Poll’s pride.
[UK] in Gentleman’s Spicey Songster [song title] Mother H’s Knocking Shop; or, A Bit Of Old Hat!
[US]N.Y. Sporting Whip 25 Feb. 1/2: The depression in the various branches of female trade has driven many amorous girls to the pave, they thinking, previous to embracing the damnable vocation, that it is a charming life, full of fun, pleasure, and devoid of all trouble. But this BARGAINING FOR OLD HAT isn’t what it is cracked up to be, which they learn to their disagreeable disappointment after a trial.
[UK] ‘The Female Auctioneer’ in Rakish Rhymer (1917) 137: And if your fond of nice— old hat, / I’ve some that you can buy.
[UK]Farmer Vocabula Amatoria (1966) 41: Bonnet, m. The female pudendum; ‘the old hat’.
[Aus]Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 106: OLD HAT [...] a vulgar name for the female article of commerce.

2. (Aus.) sexual intercourse.

[Aus]Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.].