Green’s Dictionary of Slang

the penis.

1612		Dekker O per se O N2: Euery one of them hath a peculiar Nick-name [...] as The Great Bull [...] one notable lustie Roague, who gets away all their Wenches; for this Great Bull (by report) had in one yeere, three and twenty Doxies, (His Jockie was so lustie).
1637		Dekker Canting Song in Eng. Villainies (8th edn) O3: Dimber Damber fare thee well [...] And thy Jocky bare the Bell, Glymmer on it never fell.
1648		Dekker Canters Dict. in Eng. Villainies (9th edn) n.p.: Jocky [...] m. yard.
1665		Head Eng. Rogue I 50: Jocky, A Flayle, or mans Privities.
a.1674		‘A Wenches complaint for . . . her lusty Rogue’ Head Canting Academy (1674) 17: [as cit. 1637].
1688		R. Holme Academy of Armory Ch. iii item 68c: Canting Terms used by Beggars, Vagabonds, Cheaters, Cripples and Bedlams. [...] Jocky, a Mans Yard.