Green’s Dictionary of Slang

(US) a general intensifier, damned adj. (1)

1927		(con. 1914–18) L. Nason Three Lights from a Match 181: How the hell can I fire if the christly aimin’ point blew out?
1932		E. Hemingway letter 29 Oct. in Baker Sel. Letters (1981) 375: Here at Key West after un-Christly blizzards all across Wyoming and Nebraska.
1944		H. Brown Walk in Sun 46: Don’t ask so many christly questions.
1951		R. Leveridge Walk on the Water 330: You christly, silly, stupid, goddam fool!
1966		W. Wilson LBJ Brigade (1967) 54: The copter makes a Christly racket as it violently shivers along.
1978		S. King Stand (1990) 90: Christly woman’s worse’n a jukebox with a broken record inside it.
1980		in N.E. Folklore XXVIII (1988) 23: The christly dooryard was full of them [HDAS].
2002		W. Carpenter Wooden Nickel n.p.: They found him passed out on top of the christly thing, at first they couldn’t tell which one was dead, him or the moose.