Leo Calvin Rosten was born in Lodz, Russian Empire (now Poland) and died in New York City. He was a teacher and academic, but is best known as a humorist in the fields of scriptwriting, storywriting, journalism and Yiddish lexicography.
This is at least equal parts joke book and etymology - which sounds like a delightful combination, and it is, but I ended up having to take it in such small doses that I'm returning it to the library unfinished despite having renewed it 5 times...
If you're Jewish and Ashkenazi who uses Yiddish expressions, this is the book for you. Even more so if you have parents who speak Yiddish. What I loved about this book was that it explained a lot of what Jewish culture is and why being Jewish is all about the culture as much as it is about the religion.
Rosten nominates words for Yinglish, or explains why he thinks certain phrases have Yiddish derivations. Since he spices most of his entries with jokes that use or explain the terms involved, reading this is like indulging in a jokebook.