Why is it called bierock?

A Bierock is a German-Russian meat and cabbage pastry, also called a Krautbierock, or Runza. There are variations of Bierocks which consist of cheese, ham, and other items. These delicious pastries can be found all over the United States, in Argentina, in Germany and in other areas where descendants of the German-Russians now live.

The word "Bierock" is a Germanized spelling of the Slavic word "Pirog" which originates from the Proto-Slavic word "pir" which means banquet. A Pirog is a kind of pastry that can be eaten with one hand. This suggests that culinary fusions were taking place among the German refugees who fled to the Volga region and Black Sea areas of the Tsarist Russian Empire from around the middle of the 19th Century. Other German-Russian dishes which reflect this relationship include: Koledetz, Platschentas, Borscht, and Kvass- all of which were common among the German-Russians living in German-Russian colonies.

So Bierock is merely a Germanized form of "Pirog", which is of Slavic/Russian origin. If you ever heard of "Pirogies" or "Piroshkis" these are smaller versions of the Pirog.