I suggest reading the whole article about Jews in Belarus, but this quote is what should interest you: Old principles of forming Jewish family names also became a source of many last names, now permanent and passed on by inheritance. The Hebrew names “Ben” or “Bar” became “son” (“zon”) (der Sohn - son in German). From here appeared Katz - Katznelson, Shmuel - Shmulenson, Abram - Abramson, Israelson, Davidson, and Gurshenzon.
I don't know enough about Jewish history and population movements into Central and Eastern Europe to speculate on where you would likely find relatives or more info. However, Katz obviously comes in many forms with many endings: Katzman, Katzovitz, Kasowits, Kaczowich, Katz, Katzer. (The first four names all meaning son of Katz). The best guess is that -nel- just makes it sound more Jewish or to have "cat" and "son" connect better (tzs is rather difficult to say, don't you think?).
~Infamous? I think I like that. I'll take two orders of infamous, please.http://klundtacularwrites.blogspot.comhttp://projectwritingroom.blogspot.com/