Green’s Dictionary of Slang

1. an American [Yank n. (2)].

1979		R. Barker Fletcher’s Book of Rhy. Sl.
1984		Partridge DSUE (8th edn) 1048/2: since WW2.
1989		M. Amis London Fields 81: ‘I know what you are. A four-wheel Sherman.’ An explanation was effortfully supplied. Four-wheel = four-wheel skid = yid. Sherman = Sherman tank = yank.
1993		I. Welsh Trainspotting 154: We fill in some fuckin Sherman Tank.
2002		B. Kirkpatrick Wicked Cockney Rhy. Sl.
2008		J. Niven Kill Your Friends (2009) 41: Krauts, Frogs, Shermans, Japs and Brits.

2. masturbation [wank n. (1)].

1998		I. Welsh Filth 109: I recover from that Sherman Tank with a strong cup of coffee.
2000		J. Hawes Dead Long Enough 9: Samuel Pepys had, according to his diary, a quick Sherman during the sermon while off his tits on sherry.
2003		B. Dark Dirty Cockney Rhy. Sl.