Where does “бранденбургский” come from?

бранденбургский (Russian) comes from Russian Бра́нденбург, from German Brandenburg, from German burg, from Old French burc, from Old High German burg, from Proto-West Germanic burg, from Proto-Germanic burgz, from Proto-Indo-European bʰr̥ǵʰ-.

Ancestry of “бранденбургский”, step by step

StepLanguageWordMeaning
1RussianБра́нденбургBrandenburg
2GermanBrandenburg
3Germanburgfortress
4Old Frenchburctown or city
5Old High Germanburga castle; a city
6Proto-West Germanicburgfortification; city
7Proto-Germanicburgzfortification, stronghold; city
8Proto-Indo-Europeanbʰr̥ǵʰ-
Every word from Proto-Indo-European bʰr̥ǵʰ-