Green’s Dictionary of Slang

a euph. for damned adv.

1815		D. Humphreys Yankey in England 19: No; you were too darned cute; too plaguey knowing.
1821		R. Waln Hermit in America on Visit to Phila. 2nd series 129: Had to carry aunt Tab’s lapdog—fell asleep—let it fall overboard—yell’d like an Indian—darn’d sorry it wasn’t killed—no more bore.
1824		R.B. Peake Americans Abroad I i: A pretty considerable darned out of the way beginning I’ve made in this country.
1854		Hillsdale Standard (MI) 10 Oct. 1/4: She was a darned good old thing, but not as clean as her mother.
1873		W.H. Thomes Slaver’s Adventures 29: I sell tree hundred niggers at twenty dollars apiece, and you got darned good bargain. I lose money.
1876		‘Dan de Quille’ Big Bonanza (1947) 278: All too durned high-toned!
1883		‘Mark Twain’ Life on the Mississippi (1914) 188: Derned likely story!
1898		John Fox Jr ‘A Trick O’ Trade’ in Hell Fer Sartain and Other Stories n.p.: He was a-gittin’ the land so durned cheap.
1899		Ade Fables in Sl. (1902) 182: They regarded her as a Darned Swell Girl.
1908		‘O. Henry’ ‘Squaring the Circle’ Voice of the City (1915) 131: Howdy, Cal! I’m durned glad to see ye.
1915		T. McNamara Us Boys 10 Sept. [synd. cartoon strip] Theres something darned funny about all this.
1920		E. O’Neill Beyond the Horizon I ii: I’m durned glad you’re comin’, boy.
1920		‘Sapper’ Bulldog Drummond 181: It’s a big scheme [...] a durned big scheme.
1921		D.L. Sayers Unpleasantness at the Bellona Club (1977) 110: You’re so darned clever.
1930		(con. 1900s–10s) Dos Passos 42nd Parallel in USA (1966) 328: People he talked to were darned agreeable.
1937		P. Cheyney Dames Don’t Care (1960) 22: As a case it’s durned interestin’.
1944		E.S. Gardner Case of the Crooked Candle (1958) 169: You don’t need to be so darned uncomfortable.
1953		J. Thompson Criminal (1993) 9: The commercial stuff you get down is a darned far cry from the government-contract jobs.
1968		P. Barnes Ruling Class II i: We’ve been darned lucky up to now.
1984		C. White Life and Times of Little Richard 50: We were making a darned good living.
2000		Observer Screen 23 Jan. 18: Being a teacher is darned hard work.