Green’s Dictionary of Slang

a euph. for damned adv.

1837		R.M. Bird Nick of the Woods II 106: Roar as much as you cussed please.
1840		T. Haliburton Letter-bag of the Great Western (1873) 16: Dey is cussed stupid is dem whites, and werry conceited too.
1848		‘Ned Buntline’ Mysteries and Miseries of N.Y. IV 32: It’s cussed hard to spile a rotten egg!
1875		Lancaster Gaz. 22 May 3/1: She is sich a darnation cross critter, she is so cussed contrary.
1925		S. Lewis Arrowsmith 259: You know cussed well I’d do anything to avoid —.