Green’s Dictionary of Slang

jockum n.

also jockam
[ety. unknown]

the penis.

[UK]Harman Caveat for Common Cursetours in Viles & Furnivall (1907) 87: There was a proud Patrico and a nosegent, he tooke his Jockam in his famble, and a wapping he went.
[UK]Misogonus in Farmer (1906) II iv: By promise, as you know, the old Jochum I should certify When his son from birding home did retire.
[UK]Groundworke of Conny-catching [as cit. c.1566].
[UK]Rowlands Martin Mark-all 39: Iockman a mans yard.
[UK]Head Canting Academy (2nd edn) 16: He must have a stronger stomack than I, that he hath a mind to swop his Jockum with her.
[UK]‘Rum-Mort’s Praise of Her Faithless Maunder’ in Farmer Musa Pedestris (1896) 35: Dimber damber fare thee well, / Palliards all thou didst excel, / And thy jockum bore the Bell, / Glimmer on it never fell.
[UK]Canting Academy, or the Pedlar’s-French Dict.
[UK]Scoundrel’s Dict.
[UK]Farmer & Henley Sl. and Its Analogues.
[UK]A. Crowley Snowdrops from a Curate’s Garden 21: My anus [...] attained such proportions, or rather elasticity, that I believe I could accommodate the cow-catcher of a Pacific Express, or crush the life out of the diminutive and tapering jockam of a centipede.

In compounds

jockum cloy (v.) (also jockum) [fig. use of cloy v.]

of a man, to have sexual intercourse.

[UK]Head Canting Academy (2nd edn).
[UK]B.E. Dict. Canting Crew n.p.: Jockumcloy c. to copulate with a Woman.
[UK]New Canting Dict. [as cit. c.1698].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]H.T. Potter New Dict. Cant (1795) n.p.: Jockum to have connection with a woman.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.
jockum gage (n.) (also jacum-gag) [gage n.1 (2)]

(UK Und.) a chamberpot; thus rum jockum gage, a silver chamberpot.

[UK]Head Canting Academy (2nd edn).
[UK]B.E. Dict. Canting Crew n.p.: Jockum-gage [...] Rum Jockum-gage, c. a Silver chamber-pot.
[UK]J. Shirley Triumph of Wit.
[UK]A. Smith Lives of Most Notorious Highway-men, etc. (1926) 207: Jockum-gage, a chamber-pot. Tip me the jockum-gage, i.e., hand me the member-mug.
[UK]New Canting Dict. [as cit. 1719].
[UK]Bailey Universal Etym. Eng. Dict. [as cit. 1719].
[UK]Scoundrel’s Dict. 16: A Chamber-Pot – Jacum-gag.
[UK]Grose Classical Dict. of the Vulgar Tongue.
[UK]Lex. Balatronicum.
[UK]Egan Grose’s Classical Dict. of the Vulgar Tongue.
[US]Matsell Vocabulum.
jockum-gagger (n.) (also jack-gagger, jock-gagger) [jock n.1 (1)/ jockum n. + gagger n.1 (3), lit. ‘penis-beggar’]

a man who lives on his wife’s prostitution, a pimp.

[UK]H.T. Potter New Dict. Cant (1795) n.p.: jockum gagger a set of fellows who live on the prostitution of wives.
[UK]G. Andrewes Dict. Sl. and Cant n.p.: Jock-gagger, a sort of fellows who live on the prostitution of their wives, &c.
[UK]Flash Dict.
[UK]G. Kent Modern Flash Dict.
[UK]Swell’s Night Guide 123/1: Jock gaggers, fellows who live on the prostitution of their wives.
[UK]Duncombe New and Improved Flash Dict.
[US]Matsell Vocabulum 45: jack-gagger A fellow that lives on the prostitution of his wife.
[UK]Barrre & Leland Sl., Jargon and Cant I 491/1: Jack gagger (American thieves), a man who lives on the prostitution of his wife.
Las Vegas Weekly 8 Jan. [Internet] Porn Glossary [...] Jack gagger -- A husband that procures men to pay for sex with his wife. His motivation could be: A. The recession, B. He's sick of doing the job himself.