By the way, The German words in Yiddish are not bastardized standard German, but bastardized Pfälzisch, basically the dialect where I grew up. "Gefilde Fis[c]h" is how one would pronounce "Gefüllter Fisch" there, etc.

In the middle ages, the Mainz-Worms-Speyer region was the center of Jewish life in Germany.

I think I even found a wrong explanation on that Wikipedia page, simply by knowing Pfälzisch: A "Schnook" is a housefly. It doesn't match the Yiddish meaning that well, but it's the exact same word.

Hmm! I wonder if you can correct it.