Green’s Dictionary of Slang

(orig. US) euph. for motherfucker n.

1964		Howe Valley of Fire 190: Being able to call a gook an emm-eff in pig Latin and get away with it [HDAS].
2000		K. Walker ‘The Kings of Comedy’ WalkerWorld 🌐 The ribaldry extended to a bawdy linguistic lesson on the permutations of the word emeff by Bernie Mac, who tells us it’s a noun. ‘The emeff owes me 35 emeffing dollars. I ain’t seen the emeff since. But next time I see the emeff, he better have my emeff money…’.