Green’s Dictionary of Slang

synon. for motherfucking adj.

1989		(con. 1968) W.E. Merritt Where the Rivers Ran Backward 20: Move, honky. I’m relieving you out here. Get in the mofo truck [...] Shee-it, mofo. You mofo lucky they sent me along.
1999		Indep. on Sun. 18 July 9: To blow those mo’fo’ Heffalumps to hell.