In Yiddish, shmendrik means stupid person, and yiddisher kop means smart person. More familiar are some of the American slang words taken from Yiddish expressions, including glitch, klutz, nosh, shmooze and spiel. American slang borrowed many Yiddish words from movie and play scripts, preserving spellings while sometimes altering exact meanings.
Not knowing that schmuck refers to male anatomy, non-Yiddish speakers use the word to insult a person's wisdom or judgment. In Yiddish, maven may sarcastically refer to an expert, but the word loses the sarcasm in American English. Some Yiddish expressions have evolved in spelling and pronunciation while maintaining the meaning; for example, tuches and tokhis are Yiddish words for backside that American slang recast as tush and tushy.