Green’s Dictionary of Slang

(US) a general intensifier.

1856		N.O. Weekly Delta 23 Nov. p.1 in A.P. Hudson Humor of the Old Deep South (1936) n.p.: Jo Cole sed [...] he’d be dad burned if Uncle Mike should suffer for a drink.
1873		C.H. Smith Bill Arp’s Peace Papers 48: I’ll be dad-swampd if the kommissery didn’t keep his flour in em.
1878		Sedalia Wkly Bazoo (MO) 15 Oct. 3/7: If they ever ketch him in this blasted dad burned town agin, they’ll know it.
1888		C.E. Craddock Despot of Broomsedge Cove 69: Dad-burned purty little Woolly, I’ll swear.
1888		Nye & Riley Railway Guide 13: O’ yer dad-burned old earth-quakes!
1917		Van Loan ‘Sanguinary Jeremiah’ in Old Man Curry 133: ‘You study them dad-burned dope sheets.’.
1921		Morn. Tulsa Daily World (OK) 18 Feb. n.p.: Pussyfoot’s entire journey hither was just one dadburned thing after another.
1927		K. Nicholson Barker 1: But who’d think where buildings are tall / Business could be so dad-burned bum?
1931		H. Hatcher ‘Raccoon John’ in Botkin Folk-Say 35: Dad burn the dadburned bitch to hell!
1958		L.F. Cooley Run For Home (1959) 228: I’ll be dad-burned if I can call you ‘Lewis’ on paper.
1987		‘Joe Bob Briggs’ Joe Bob Goes to the Drive-In 212: If Chloris wasn’t so dad-burned anxious to put one of those plastic swords on the end of her trick finger, this wouldn’t never happened.
2000		Guardian 14 Nov. 22: I about had a cotton-pickin’ stroke. I hollered for my wife and I said, ‘The dadburned ballots are still in the car’.