From the Yiddish dictionary; please notice second dictionary entry from the top:

• schmuck : a contemptible or foolish person; a jerk; literally means 'penis' (from Yiddish שמאָק shmok 'penis')
• schmutter : clothing; rubbish (from Yiddish Yiddish שמאַטע shmate 'rag', as above)
• schmutz - dirt (from Yiddish שמוץ shmuts or German Schmutz 'dirt')
• schnook : an easily imposed-upon or cheated person, a pitifully meek person, a particularly gullible person (perhaps from Yiddish שנוק shnuk 'snout')