According to the Merriam Webster Dictionary;

Schmuck : schmuck
Pronunciation: 'shm&k
Function: noun
Etymology: Yiddish shmok, literally, penis
Date: 1892

Schmuck, a Yiddish word, has a range of meaning depending on context. In its most innocuous use, a schmuck is a person who does a stupid thing, in which case “dumb schmuck” is the appropriate expression.

A schmuck's behavior ranges from pesky and inconsiderate, to obnoxious and manipulative. A schmuck's personality type ranges from jerk to bastard.

Schmucky behavior also falls within a range of intentionality. Some schmucks carefully plan their bad behavior, some only a little, and some not at all. For example, the bastard may spend considerable time planning his bad deeds. In contrast, the dumb schmuck and the pesky behave badly without any forethought.