Why are they called “knishes”?

“Knish” is a Yiddish word, Yiddish being a Germanic language created by Ashkenazi Jews who settled in and around the Rhine Valley about the year 900. It closely resembles two other words in current use today, the Russian knys which means “pastry” and the Polish knyz meaning “snack.” Put those two together, and that’s pretty much a knish. Were Old World knishes like anything like New World knishes? That’s where the picture gets fuzzy. But then I’m not sure, save for a short period in the early part of the 20th century, that the concept of the knish has ever been in very sharp focus. “A (usually) baked snack” may be as precise a definition as I can muster. (Thanks to readers Chana and Jim).