Green’s Dictionary of Slang

(US) a euph. for motherfucker n.

1948		Manone & Vandervoort Trumpet on the Wing 70: I’ll be a motheree if I’ll wear any damn bedpan intern’s suit.
1959		W. Miller Cool World (1965) 15: I have the blade in my hand open and ready. Motherens. Come at me you Motherens.
1967		in S. Harris Hellhole 130: Anything happen to my baby, I find you motheren coppers wherever you at [...] You son of a bitch coppers. You motherens.