Why do Russian Jews have German names?

The language of the Jews throughout eastern Europe was Yiddish. Yiddish is in large part derived from an old form of German.

When the Jews of eastern Europe were required by their local governments to take surnames during the early and middle 19th century, many of them were able to choose their own names. Often they used patronymics, nicknames, or other terms from their Yiddish language.

The names of Russian Jews are often Yiddish in origin, but because Yiddish has much in common with German, the uninformed think they are German names.