jocko, n. — Green’s Dictionary of Slang

jocko n.

[generic use of name Jock but ? dial. jockey, a peasant, a countryman]

(US)

1. a stupid or contemptible man or boy; also a term of address.

1926		(ref. to 1918) F. MacIsaac Tin Hats n.p.: Ain’t got a nose ring? [...] I’ll give a nose ring, Jocko.
1968		K. Brasselle Cannibals 53: He wasn’t going to make a ‘jocko’ out of me.
1989		C. Hiaasen Skin Tight 28: ‘His name’s not Jocko’ ‘He’s a circus ape, that’s a fact.’.
2000		P. Beatty Tuff 53: Listen, jocko, I want yellow bananas, not these unripe, snot-green plátanos.

2. (US) an African-American.

1955

B. Appel Tough Guy [ebook] They [...] fought off five jockos in a St. Louis flop who wanted their white skin.

3. a friendly form of address.

1959		E. De Roo Go, Man, Go! 40: Give her a break, jock-o.
1963		H.S. Thompson letter 15 Aug. in Proud Highway (1997) 385: An odd twist to report on this front, Jocko.
1976		P. Conroy Great Santini (1977) 237: Don’t forget, jocko, I want you to meet me at the club at 1700 hours.