Green’s Dictionary of Slang

of British women, to pick up American servicemen during WWII; thus Yanking n.

1950		P. Tempest Lag’s Lex. 233: Yanking. Popular expression to describe the activities of girls who specialise in picking up American soldiers.
1984		Partridge DSUE (8th edn) 1359/1: [...] since 1943; by 1966, slightly ob.