Green’s Dictionary of Slang

buttonhole n.

the vagina.

[UK] ‘The Button Hole’ in Button Hole Garland 2: I’m a Hole, tho’ too narrow, / When first I am try’d, / Yet the thing I am made for / Can stretch me out wide.
[UK]Harris’s List of Covent-Garden Ladies 58: ’Tis true you was always remarked for a button-hole.
[UK]‘Roger Ranger’ Covent Garden Jester 86: May every good button find a good button-hole.
[UK]‘Medley’ in Hilaria 39: Poor Jack, the Brighton taylor, / For stitching well a button-hole, was pinned up by the jailor.
[US]Ely’s Hawk & Buzzard (NY) Mar. 22 2/2: pseudonym in ‘sporting’ paper letters' column: peggy buttonhole.
[UK]‘Toasts’ in Gentleman’s Private Songster in Spedding & Watt (eds) Bawdy Songbooks (2011) III 383: The royal button manufactory, and may every good button find a good buttonhole.
[UK]Bacchanalian Mag. 74: Original and selected Toasts and Sentiments [...] May a good button-hole never want a stout button.
[UK]Peeping Tom (London) 12 48/3: [advert] jolly companion — Button Hole.
[UK]Farmer & Henley Sl. and Its Analogues.
[UK]Farmer Vocabula Amatoria (1966) 45: bouton, m. [...] 2. The female pudendum; ‘the button-hole’.
[US]B. Appel Tough Guy [ebook] A girl was either a whore or she was up on a pedestal a million miles high, wearing a snowcloud for a coat and burglar-proof locks at her buttonholes.

In compounds

buttonhole factory (n.)

a brothel.

[UK]‘Toasts’ in Gentleman’s Private Songster in Spedding & Watt (eds) Bawdy Songbooks (2011) III 383: The royal button manufactory, and may every good button find a good buttonhole.
[US]D. Lypchuk ‘A dirty little story’ in eye mag. 8 July 🌐 Of course, she had no idea that his shag slab was such a buttonhole factory.
buttonhole prick (n.)

(US) a large penis.

Actionable Offenses ‘The Whores’ Union’ (2007) [cylinder recording ENHS 30188] NB--Liberal allowance is made for button-hole pricks, commonly called cunt robbers, hair curlers, liver disturbers, kidney wipers, belly ticklers, bowel starters, etc. Anything above fourteen inches barred out.

In phrases

stitch buttonholes (n.) (also make buttonholes)

of a man, to have sexual intercourse.

[UK]D. Gunston (ed.) Jemmy Twitcher’s Jests 6: While one great personage spends his time in making buttons, another [...] thinks nothing else but stitching button holes.
[US]Flash 31 July n.p.: Norwich, Conn. Wants to Know [...] What Lon L was doing with Mary P in that lumber yard — was he making buttonholes.

SE in slang uses

In compounds

buttonhole cousin (n.) (also buttonhole connection, bottonhole kinfolks, buttonhole relation) [ety. unknown; ? one SE buttonholes them and claims a relationship]

(US) a distant relation (e.g. a third or fourth cousin), a family friend.

[US]G.D. Chase ‘Lists From Maine’ in DN IV i 4: buttonhole connection, or relation, n. A person but slightly or remotely related.
[US]Randolph & Wilson Down in the Holler 119: One may use button-hole cousins, or button-hole kinfolks, without offence.
buttonhole maker (n.)

a woman.

[US](con. 1948) G. Mandel Flee the Angry Strangers 142: He has a grudge against her for not being a boy. His father calls him a buttonhole maker, and he does a slow burn.