are we talking like, in comon use? and among the Ashkenazim?
It's a patronymic naming culture (check out a ketubah next time you're at a Jewish wedding, it probably uses this naming convention still) that lost that convention in civic spaces over time.
Surnames are a product of voluntary (if one counts voluntarily hiding their identity as being voluntary) and coerced assimilation during diaspora. Germanic and Slavic surnames are "common" in Jews (I think Miller is the third most popular "Jewish" surname in the U.S.
) because of a decree issued in the Austro-Hungarian Empire in the late 18th century and because the Commonwealth was a European rarity in that you could actually be Jewish and not murdered on a whim while living there.
Cohen (plus variants) and cantor are Jewish trades. Logically speaking it follows that one would not adopt a trade-based surname of that nature if one was not Jewish at the time.
People say some of the old tribes used as surnames count as Jewish ones too (e.g. Levy, Israel) but cacs love to be fucking biblical so I don't really buy that.
e: Some additional research tells me there's a suite of religious occupation names in addition to Cohen and Cantor, so I guess those count too under my line of reasoning. I ain't heard of half of these doe.
