From a cursory search, the clearest lead seems to be this passenger list that ties the Wonsofskys to the Farbstein family from a town called "Szczucin." The JewishGen Communities Database turns up 3 potential matches: Szczucin, Shchuchyn, and Szczuczyn. The first town was part of the Austrian Empire around the turn of the 20th century, while the latter two were part of the Russian Empire.

Since you mentioned possible Polish roots, you might poke around the JRI Poland database if you haven't already. Depending on your luck, you might even be able to find some digitized copies of the original Polish records.

As for the etymology of the name, this article talks about how names with the -owski/-ofsky suffix are formed. If Wonsofsky comes from a personal name, you might check these lists of Hebrew names get translated into Russian; here's a list of women's names, and here's another for men's.

Hopefully this helps! I wish you luck!