Green’s Dictionary of Slang

gait n.

(US) one’s trade, occupation.

1859		Matsell Vocabulum 35: ‘I say, Tim, what’s your gait now?’ ‘Why, you see, I’m on the crack’ (burglary).
1865		‘Mark Twain’ Sketches New and Old 74: Preachin’ was his nateral gait, but he warn’t a man to lay back [...] because there didn’t happen to be nothin’ doin’ in his own especial line.
1881		Trumble Sl. Dict. (1890).
1889		Farmer Americanisms 257/1: In the patter of the criminal classes, one’s gait does not so much refer to style or pace in walking, as, by a curious transition, to one’s ‘walk in life’; calling; trade; profession—in short, the manner of making a living is one’s gait.

In phrases

get a gait on (v.)

()

1947		J.F. Powers ‘the eye’ in Prince of Darkness 187: ‘Tonight I just feel like stringing me up a black nigger by the light of the silvery moon! Let’s get gaiting!’.
1961		(con. 1930s) D. Behan Teems of Times and Happy Returns 204: ‘Well,’ he snapped, ‘what the hell are yeh gaiting for?’.