they had no surnames until late 18th and early 19th century. they could choose one themselves or were assigned a surname if they didn't cooperate. when they chose one themselves it was usually something vain ("good man", "rich = reich", "gold mountain = goldberg"). when they we're forced to take one it was often something insulting (klein = small, wexler = moneychanger). a big fraction chose toponyms of the german counties they traditionally lived in: katzenellenbogen, frankfurter, rosenberg, ladenburg, cassel etc. the surname is usually insufficient to identify jews, but is a strong clue. feds are going to mislead and demoralize you by constantly creating false positives, usually attacking every news-relevant american with a german surname for d&c purposes.
Germany