The baptism registers for the children of Marcin Szczepański and Anna Kalinowska at St. Stanislaus parish in Buffalo, New York, from 1884 to 1898 list the parents’ place of birth as Szombrug, Szömbrug, Szenbruk, Szenburg, Szönbruk, Szymbruczek or a variation.
Since umlauts are not used in Polish or Latin, it looks like these are versions of a German name, so it probably begins with SCH instead of SZ. Marcin Szczepański was fluent in both German and Polish, and his 1931 obituary said he had come from Germany. Anna‘s obituary in 1938 said she was from Poland. We know they were married in 1878, because they celebrated their 50th wedding anniversary in 1928.
Borussia is the Latin name for Prussia. Since other locations in the parish registers are Galicia and Posen (identified specifically), they probably came from West Prussia, East Prussia, or Silesia. Here is a Wikimedia map of Prussia at that time.
I suspected the German version of the names in Prussia would be Schomberg, Schömberg, or Schoenberg. When I did my original research in the 1990s, I found small towns that had been known as Schomberg in southern Poland near the border with the Czech Republic, so that is where I thought they were from.
More recently, I was able to research Kartenmeister.com and found that there are even more possibilities for former Prussian places currently in Poland that had used the German names Schomberg, Schömberg, or Schönberg.
More research is needed.