Green’s Dictionary of Slang

a euph. for fuck v. in various senses; also as a n.

1945		J. Maclaren-Ross Swag, the Spy and the Soldier in Lehmann Penguin New Writing No. 26 (1945) 31: Then he muttered: ‘Fog ’em.’ ‘What’s wrong, Sandy?’ I asked him. [Ibid.] 43: ‘Ah, for fog’s sake,’ he said.
1954		(con. 1940s) E. Lambert Veterans 128: Fog yer! [Ibid.] 147: Get fogged! [Ibid.] 163: Well, I’ll be fogged!
1958		(con. 1940s) B. Behan Borstal Boy 216: ‘Foggem all,’ said Chewlips.
1959		(con. 1940s) E. Lambert Glory Thrown In (1961) 30: ‘Fog Hitler!’ said the sentry.
1964		R. Helmer Stag Party 81: Wull, fog my bloody days, eh?