Green’s Dictionary of Slang

(US) a euph. substitute for damnation! excl.

1787		R. Tyler Contrast V i: Tarnation! That’s no laughing matter though.
1824		R.B. Peake Americans Abroad I i: Tarnation! that Uncle Ben, he always doos.
1829		Chester Courant 22 Dec. 4/1: ‘Bugs and tarnation!’.
1840		R. Barham ‘Lay of the Old Woman Clothed in Grey’ in Ingoldsby Legends (1842) 267: While she uttered that word, / Which American Bird, / Or John Fenimore Cooper, would render ‘Tarnation!!’.
1865		G.A. Sala My Diary in America II 288: Blarnation! nary ticket. Cast me loose.
1886		Washington Standard (Olympia, WA) 30 June 6/2: ‘Tarnation to ye!’ cried Weeks.
1905		‘Central Connecticut Word-List’ in DN III:i 22: tarnation! interj. An oath.
1969		P. Theroux Murder in Mount Holly (1999) 87: ‘Tarnation,’ Mr Gibbon said.