The colours Black and White were originally the colours of the Teutonic knight order, which had once founded a monastic state in East Prussia. Later the prince-electors of Brandenburg, the family of the Hohenzollern (who coincidentally also had Black and White as colours of their house), got the territory and used the same colours for the new duchy of Prussia. The colours were then adapted when the Hohenzollern were proclaimed kings in (and later "of") Prussia, referring to the former order state of Prussia because their original territory of Brandenburg could not be a direct kingdom due to it still being part of the Holy Roman Empire.