Green’s Dictionary of Slang

sherman (tank) n.

[rhy. sl.]

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

[UK]R. Barker Fletcher’s Book of Rhy. Sl.
[UK]Partridge DSUE (8th edn) 1048/2: since WW2.
[UK]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.
[UK]I. Welsh Trainspotting 154: We fill in some fuckin Sherman Tank.
[UK]B. Kirkpatrick Wicked Cockney Rhy. Sl.
[UK]J. Niven Kill Your Friends (2009) 41: Krauts, Frogs, Shermans, Japs and Brits.

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

[UK]I. Welsh Filth 109: I recover from that Sherman Tank with a strong cup of coffee.
[UK]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.
[UK]B. Dark Dirty Cockney Rhy. Sl.