Green’s Dictionary of Slang

a euph. for god-damned adj.; thus gorm v, to damn.

1849		Dickens David Copperfield (1991) 312: Gorm the t’other one. [Ibid.] 869: If a ship’s cook [...] didn’t make offers fur to marry Missis Gummidge, I’m Gormed.
1856		Leicester Jrnl 1 Aug. 4/1: Well, oi’m giormed if oi ever!
1864, 1867, 1870		Hotten Sl. Dict.
1868		Pall Mall Gaz. 2 Sept. 9/2: You showed me all that [...] and gallows nice it looked. But I’m gormed if i find my pockets any warmer.
1873		Leeds Times 13 Dec. 6/1: Jim he were a sight. He was gormed.
1883		Punch 19 May 230, col. 2: Why, of course, I hardly expects to be believed but I’m gormed if there was more than six of one and half-a-dozen of the other.
1894		London Graphic 1 Dec. 15/3: Since the time when Mr Peggotty said, ‘he’d be gormed if he would,’ little novelty has been introduced into [...] our vocabulary.