Many of the names that people think "sound" Jewish are, in fact, simple German, Russian or Polish surnames. The point? You generally can't identify Jewish ancestry by a surname alone. Actually, there are really only three surnames (and their variations) that are generally specifically Jewish in nature: Cohen, Levy and Israel. Yet, even variations of these common Jewish-specific surnames may not be Jewish. The surnames Cohan and even Cohen, for example, could indeed be Jewish in origin; but could also be an Irish surname, derived from O'Cadham (descendant of Cadhan).
While few names are specifically Jewish, there are certain surnames that are more commonly found among Jews:
- Names ending in -berg (Weinberg, Goldberg)
- Names endin in -stein (Einstein, Hofstein)
- Names ending in -witz (Rabinowitz, Horowitz)
- Names ending in -baum (Metzenbaum, Himelbaum)
- Names ending in -thal (Blumenthal, Eichenthal)
- Names ending in -ler (Adler, Winkler)
- Names ending in -feld (Seinfeld, Berkenfeld)
- Names ending in -blum (Weissblum, Rosenblum)
- Names having to do with wealth (Goldberg, Silverstein)
- Names derived from Hebrew words (Mizrachi, from mizrakhi, meaning "eastern, or easterner")
Estee Reider, in Jewish World Review, also points out that some Jewish surnames may originate from professions that are exclusive to Jews. The surname Shamash, and its variations such as Klausner, Templer and Shuldiner, means shamash, a synagogue sexton. Chazanian, Chazanski and Chasanov all derive from chazan, a cantor.
Another common origin for Jewish surnames are "house names," referring to a distinctive sign attached to a house in the days before street numbers and addresses (a practice in use primarily in Germany, by both Gentiles and Jews). The most famous of these Jewish house names is Rothschild, or "red shield," for a house distinguished by a red sign.
As I said before, you can't assume that any of these name are Jewish, no matter how Jewish they may sound to you, or how many Jews you know with that name. The third most common Jewish surname in America (after Cohen and Levy) is Miller, which is also obviously a very common surname for Gentiles as well.
More in-depth discussions of Jewish surnames can be found at Jewish Names from Judaism 101, History of German Jewish Surnames: Is My Surname Jewish? by Esther Bauer, PhD, and The Names of the Jews by Joachim Mugdan at JewishGen.