Green’s Dictionary of Slang

jocky n.1

[jockum n.]

the penis.

[UK]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).
[UK]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.
[UK]Dekker Canters Dict. in Eng. Villainies (9th edn) n.p.: Jocky [...] m. yard.
[UK]Head Eng. Rogue I 50: Jocky, A Flayle, or mans Privities.
[UK] ‘A Wenches complaint for . . . her lusty Rogue’ Head Canting Academy (1674) 17: [as cit. 1637].
[UK]R. Holme Academy of Armory Ch. iii item 68c: Canting Terms used by Beggars, Vagabonds, Cheaters, Cripples and Bedlams. [...] Jocky, a Mans Yard.