'Königs Wusterhausen' means 'the King's Wusterhausen'.
Until 1718 the town was called Wendisch Wusterhausen. The future 'Soldier King' Friedrich Wilhelm I received its castle as a gift for his tenth birthday in 1698 and had it rebuilt as a hunting lodge; in 1718, when the lodge was inaugurated, the place was renamed. 'Wusterhausen' itself is thought to come from a Slavic word for a palisaded stronghold.