As we say here in the South, "Leben ahf dein kop!"
Incidentally, the most comprehensive listing I've found of Yiddish words and expressions on the Web is Michael Fein's at
www.pass.to/glossary/gloz2.htm It's many pages long, but sheds no further light on the "krep-" question. What you've done here is probably as good as it gets.
And judging by the tone of Fein's list, these were not an "up", bubbly group of people, were they? Guess life in the shtetl does that. (Reminds me of my Scottish, blue-collar grandfather, whose favorite expression was "what they don't give ye, ye don't have ta thank 'em for".)