Green’s Dictionary of Slang

(US) a stable-boy.

1917		Van Loan ‘Playing Even with Obadiah’ in Old Man Curry 56: Slipped it [i.e. a weight pad] to that big nigger swipe of his.
1929		S. Anderson in Mercury Story Book 221: I had taken a job as swipe with one of the two horses Harry was campaigning [DA].
1933		W.R. Burnett Dark Hazard (1934) 44: Swipes walking the blanketed horse round and round.
1953		A.J. Liebling Honest Rainmaker (1991) 43: Trainers, Grooms, Swipes and Gallop Boys.
1954		(con. WWII) W. Faulkner Fable 178: He hasn’t got any money [...] What little there might have been, that cockney swipe threw away long ago on whores and whisky.