The name derives from when, after the fall of Duke Henry the Lion in 1180, the medieval Duchy of Saxony dissolved and the Duchy of Saxe-Wittenberg lands passed to the House of Ascania and later to the Wettins in the Margraviate of Meissen. These dynasties subdued the areas east of the Saale river inhabited by Polabian Slavs, and took the tribal name Sachsen (Saxons) upstream the Elbe with them.