That's just a nickname, they are called Maultaschen 99.9% of the time.

https://en.wikipedia.org/wiki/Maultaschen

They are basically very large ravioli, but with a more German flavor (for lack of a better word). As far as I know, the origin story is more legend than fact, but it's a funny anecdote nevertheless.

Very tasty, I recommend giving them a try if you ever have the chance. Vegetarian and vegan versions are available BTW (at least in Germany).