Green’s Dictionary of Slang

(US) a euph. for hell; esp. in a variety of phrs., e.g. what in thunderation...?; note adv. use in cit. 1836.

1836		Crockett’s Yaller Flower Almanac 21: I don’t know as I can say he was so all darned thunderation fat [DA].
1887		Manchester Eve. News 5 Nov. 4/2: I’d just like to know how in thunderation that youngster kicks out his shoes so fast.
1899		Dly Gaz. for Middlesborough 2 Sept. 4/4: ‘Great thunderation!’ ‘It is you, Cap’n, and no mistake’.
1911		R.D. Saunders Colonel Todhunter of Missouri 17: What in thunderation is the matter, suh? [DA].
1934		O. Strange Sudden 54: Jim, I’m almighty glad to see yu, but what in thunderation brung yu to these parts?
1944		W. Blair Tall Tale America 2: But where in thunderation is Japan?
1949		Sat. Eve. Post 9 July 86/2: Why in thunderation does he have to play such a hay-in-the-hair? [DA].
1957		R. Prather Always Leave ’Em Dying 43: Who in thunderation are you?