Green’s Dictionary of Slang

(US) a euph. for damn v.; thus used in mild oaths, e.g. consarn it!

1822		W.T. Moncrieff M. Tonson II.i: Nap. Why, hang me! if it an’t Mounseer Powder-blue, the barber. What's in the wind now? Consarn it! I hope there hasn’t been no rogues breaking in.
1829		London Eve. Standard 12 Nov. 4/4: Yankee Courtship [...] Consarn it, how a buss will crack a still frosty night.
1833		C.A. Davis Letters of Major J. Downing (1835) 81: He’s afraid they’ll git him in a tangle — consarn ’em.
1842		Columbia Democrat (Bloomsburg, PA) 14 May 1/5: Consarn me, if I know what the old man is going at; we’ve done all human nature can do.
1847		Lancaster Gaz. (OH) 10 Sept. 1/3: O Brother Bedoff! it’s a hyneous and a cryin’ sin — Consarn it!
1849		Lower Sandusky Freeman (Freemont, OH) 22 Sept. 1/5: I can’t give you any idea how consarned handsome everything was.
c.1850		F.M. Whitcher Widow Bedott Papers (1883) 8: Most men would a swore, but husband dident. He only said, says he, ‘Consarn it.’.
1854		Perrysburg Jrnl (OH) 2 Sept. 1/3: ‘Has he broke out?’ said the Judge. ‘Yes, and off, consarn him,’ said the prisoner.
1860		Carrollton Sun (Jefferson, LA) 30 June 1/4: Consarn it, why the bullfrogs [are] bellowing out ‘Old Abe — Old Abe’.
1870		Barnsley Chron. 26 Mar. 6/1: ‘He put his finger up his nose and axed me if my father know’d I was out [...] consarn him!’.
1881		Dodge City Times (KS) 17 Nov. 1/1: If they are out robbing trains again I’ll take the hide off o’ them [...] consarn them!
1893		H.A. Shands Speech in Mississippi 24: Consarned [...] This is a favorite expletive among the lower classes of whites. They say: ‘I’ll be consarned if it ain’t so.’.
1896		Courier (Lindoln, NE) 17 Oct. 2/4: Consarn it, it’s a useless expenditure of the people’s money.
1898		Bourbon News (Paris, KY) 29 Mar. 6/2: ‘Bears be durned,’ I hollered [...] ‘Consarn ’em’.
1903		Monroe City Democrat (MO) 22 Oct. 3/4: Consarn that Jonas!
1913		Day Book (Chicago) 18 Aug. 18/1: Consarn it! I like you, for all my rough talk.
1921		New Ulm Rev. (MN) 13 Apr. 6/1: A member of the Police [...] asked the visitor: ‘What about your tail-light?’ ‘Did the consarn thing go out again?’ replied the man in the car.
1939		W.C. Haight ‘Small Town Life’ in Mss. from the Federal Writers’ Project 🌐 Slang phrases I remember are pretty much the same today. Although we never used nearly as many as they do now: Golly dingit, Gosh darnit [...] Carnsarn it.