Green’s Dictionary of Slang

1. an evasive or contrived response.

1940		J.H. O’Hara Pal Joey 74: She gave me the routine about father & mother being in London.
1956		J. Stearn Sisters of the Night 11: One night he gave me the routine.
1960, 1975		Wentworth & Flexner DAS.
1981		J. Ellroy Brown’s Requiem 56: The ‘fourth man’ routine was just a dodge to beat the death penalty.

2. a fraudulent scheme, esp. as practised by confidence tricksters.

1947		B. Schulberg Harder They Fall (1971) 116: You know the routine.
1953		‘William Lee’ Junkie (1966) 125: The Black Bastard worked the crucifix routine.
1961		M. Braly Felony Tank (1962) 47: You know what? It’s all a big routine.
1978		(con. 1963) J. Carroll The Basketball Diaries 23: [T]hey’ll always pass up anyone else and come right over to me either [...] bumming coin or worst of all the old sob routine.
1983		A-Team Storybook 34: Don’t try that mosquito routine, sucker!