Green’s Dictionary of Slang

picklock n.

the penis.

1625		Massinger Unnatural Combat I i: This being the pickelocke That never fails.
1653		Urquhart (trans.) Gargantua and Pantagruel (1927) I Bk I 44: And some of the other women would give these names, my Roger, my cockatoo, my nimble-wimble, bush-beater, claw-buttock, evesdropper, pick-lock, pioneer, bully-ruffin, smell-smock, trouble-gusset, my lusty live sausage.
1748–49		Cleland Memoirs of a Woman of Pleasure (1985) 75: The soft oil’d wards can no longer stand so effectual a picklock, but yield and open him an entrance.
1837/8		‘The Lady’s Snatchbox’ in Cuckold’s Nest 26: The gents bring their long picklocks, / And, after I’ve polished them up, / They can open my hairy snatch box.
1865		‘Cupid Turned Housebreaker’ in Rambler’s Flash Songster 39: What would they say, if they could see, his picklock out of sight; / The ladies’ all, both great and small, how they turn up their eyes, / They’d never dreamt, his instrument was half the size.
1890–1904		Farmer & Henley Sl. and Its Analogues.
[2000		P. Howard Miseducation of Ross O’Carroll-Kelly (2004) 42: She’s one of those birds who wants to go out on, like, dates before she’ll let you pick her lock].