Green’s Dictionary of Slang

(US) a merchant seaman, a sailor in the US Navy.

1942		Honolulu Star Bull. (HI) 28 Nov. 6/1: Apprentice seamen automatically become ‘swab jockeys’.
1953		L. Uris Battle Cry (1964) 52: She won’t sleep with no swab jockies the minute your back is turned.
1960		W. Styron Set This House on Fire 300: About as graceful as some swab jockey on liberty.
1970		D. Ponicsan Last Detail 99: I bet you don’t, you freaky swab jockey.
1978		(con. WWII) T. Sanchez Hollywoodland (1981) 72: Those swab jockies got to be made of steel to fight them Jap subs and Zeros.
1985		Florida Today (Cocoa, FL) 28 July 1/1: Showing exceptional good judgment for a swab jockey (a term of endearment used by us Marines to describe sailors).