Green’s Dictionary of Slang

malformy n.

[? euph. for motherfucker n.; SE malformed]

(US black) a general insult.

[US]‘Soulful Spider’ ‘Pimp in a Clothing Store’ in Milner & Milner (1972) 286: Yessiree, Jack, he’s coming on down high-sidin’ [...] hollering, ‘Hey, you jive malformies, you better get on your job out there, quit your chippying!’.