ETYMOLOGY:
From Yiddish nebekh (poor, unfortunate), of Slavic origin. Ultimately from the Indo-European root bhag- (to share) that is also the source of baksheesh, Sanskrit bhagya (good fortune), and words related to -phagy (eating), such as onychophagia and xerophagy.
The only famous nebbishes are fictional characters: George Costanza, Isaac Bashevis Singer's Gimple the Fool, George McFly in Back to the Future, and virtually anyone played by Woody Allen or Rick Moranis.
Favorite Rick Moranis line from Ghostbusters-
'Gozer the Traveler. He will come in one of the pre-chosen forms. During the rectification of the Vuldrini, the traveler came as a large and moving Torg! Then, during the third reconciliation of the last of the McKetrick supplicants, they chose a new form for him: that of a giant Slor! Many Shuvs and Zuuls knew what it was to be roasted in the depths of the Slor that day, I can tell you!'
