William Safire, claiming a higher authority, Sol Steinmetz, says these are the top ten Yiddish words in English:
According to Sol, a data-bank search shows klutz to be among the Top 10 Yiddishisms in English. The others: glitsch, kosher, bagel, maven, mensch, schlock, schmooze, tush and chutzpah.
I can't believe that! glitch doesn't seem like a Yiddish word to me, anyway. And I kind of dispute bagel--I think it's German. And maven and kosher, it can be argued, are Hebrew words. But my candidates for the most popular yiddishisms are: meshuggah, shlemiel, shlemozzle, dreck, schmatta, putz, balebusta, mensch, shlock and tush--in any order you like.