shmuck

Shmuck is a Yiddish-derived insult meaning a foolish, contemptible, or objectionable person.

The word literally means penis in Yiddish, though most English speakers use it without awareness of this origin.

It falls somewhere between mild and moderately offensive, roughly equivalent to jerk or asshole depending on context.

Don't be such a shmuck.

The spelling schmuck is more common.