Green’s Dictionary of Slang

gosh-darn v.

(US) a euph. for god-damn v.; used in excls. and mild oaths.

1883		Sweet & Knox On a Mexican Mustang, Through Texas 253: ‘Well, gosh darn it!’ said our captor.
1905		J. London ‘All Gold Canyon’ Complete Short Stories (1993) II 1024: Gosh darn my buttons! if I didn’t plumb forget dinner!
1907		Carr & Chase ‘Word-List From Eastern Maine’ in DN III:iii 244: goshdarn it, interj. Softened form of God damn it.
1914		J. London Burning Daylight 217: Well, I’ll be plumb gosh darned!
1919		F. Hurst ‘White Goods’ in Humoresque 159: Gosh darn her neck!
1920		R.J. Fry Salvation of Jemmy Sl. I ii: Gosh durn it all, anyway.
1921		Dos Passos Three Soldiers 404: Gosh darn it, I don’t see how you can go around with a guy an’ drink with him, an’ then rob him.
1936		(con. 1920s) Dos Passos Big Money in USA (1966) 800: He’d [...] say to himself goshdarn it, he had to get him a woman of his own.
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.
1946		(con. 1910s) J. Thompson Heed the Thunder (1994) 234: You don’t have to pay for it all, gosh-darn it.
1961		(con. 1945) G. Forbes Goodbye to Some (1963) 68: Mr. D., free to take up his inner life of consumer-research prejudices [...] will be down in the cellar gosh-darning the new lawn mower.

In exclamations