It is true that German names are assumed to be jewish which is weird because like half of white americans have German ancestry. There are lot more goys with German names.

One thing I've noticed is that whites tend to have anglicized their name at some point, while jews didn't. You can see how this would lead to more of an association between German names and jewishness.

Part of this is when people came over. Massive German immigration happened when people were more blending in. By the time Euro-jews started coming en masse, we were near multiculturalism.