Same as potz or putz, ie., the male sex organ or a very stupid and foolish person. The relationship between the organ and a person derives from the Yiddish "explanation", "Wherever you push him that's where he goes". (It's better in Yiddish.) Also used as the plural of potz/putz.
"What a petz! He's such a fool he'll do any stupid thing someone tells him to." And, "What petz they are".