Green’s Dictionary of Slang

bung it (in) n.

gin.

1960		J. Franklyn Dict. of Rhy. Sl.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1984		Partridge DSUE (8th edn) 157/2: since ca. 1920s.
1992		R. Puxley Cockney Rabbit.