an intensifying expletive; a eupehmism for damned; as, for no darned reason at all.

expletives used informally as intensifiers; "he's a blasted idiot"; "it's a blamed shame"; "a blame cold winter"; "not a blessed dime"; "I'll be damned (or blessed or darned or goddamned) if I'll do any such thing"; "he's a damn (or goddam or goddamned) fool"; "a deuced idiot"; "tired or his everlasting whimpering"; "an infernal nuisance"