Know how to use "fewer" and "less"? Find out.
1960s, probably an alteration of pussy (n.2). DAS suggests shortened from hypothetical pussy-wussy, reduplicated form of pussy (n.1).
1982, abbreviated from wussy.
Mike Damone: You are a wuss: part wimp, and part pussy ["Fast Times at Ridgemont High" script, 1982]
that's all she wrote