South Slavs you guys had great migration from White Croatia, White Serbia during medieval era. If you want read about this, I belong to this coat of arms and we are I2A-DIN. This people is nobility of Carpatho-Rus. Some of the people who belong to this originated from Saxony, east Germany the region you referencing, but were Slavs. The second option for that spot of I2A-DIN in east Germany, people from Carpatho-Rus rich in I2A-DIN migrated to west Poland after WW2 my family is example, some of them take jobs in Germany, Czech on other side of border for economic reason and just remained there. There is people in my own family did this.
https://en.m.wikipedia.org/wiki/Sas_coat_of_arms