In order to find information about my ancestors, I accessed a Catholic church register of a village in the upper part of Silesia, via Family Search. The village, Śmicz, was Polish but was part of Prussia (and, from 1871, the German Empire). The records are from the 1820-1939 time period.
All the records are in German, which is not surprising, considering it was the official language.
What is however more surprising, is that while there is traces of Polish family names, there is absolutely no trace of Polish given names to anyone in the village.
By Polish given names, I mean all the series which ends in -sław, but also other typically Slavic names such as Boris, Marek, Casimir, Lech, etc...
Most given names were extremely unoriginal names that could be used in all languages, such as Joseph, Maria, etc... Not only that, but also some German names, which I do not think can be translated in Polish, were frequent, such as: Georg, Franz, Franziska, Cecilia, Emmanuel, etc...
So, how to explain that? Was there a law that prevented people giving Polish surnames to babies, or were the typical Slavic names just not in fashion in the 19th and early 20th centuries?