Green’s Dictionary of Slang

-wad sfx

[? wad n.4 (1)]

(US campus) an all-purpose usu. negative sfx that can be added freely to any word to mean a fool, e.g. asswad, stainwad.

[US]Eble Campus Sl. Fall 5: wad – suffix – derogatory ending denoting denseness, dullness, foolishness, etc. on the part of the person named: Joe is such a nerdwad.
[US]Eble Sl. and Sociability 30: -wad ‘dense, foolish person (usually attached to a proper noun)’ (‘Mikewad here locked himself out of his room’).
[US]C. Hiaasen Skinny Dip 37: Every scheming shitwad in America turned up here sooner or later.