The name 'Belgium' comes from "Gallia Belgica". This was a Roman province in the northernmost part of Gaul. Before Roman invasion in 100 BC, the "Belgae", a mix of Celtic and Germanic peoples, lived there. The Germanic Frankish tribes during the 5th century brought the area under the rule of the Merovingian kings. A slow shift of power during the 8th century led the kingdom of the Franks to change into the Carolingian Empire. The Treaty of Verdun in 843 divided the region into Middle and West Francia. They were vassals either of the King of France or of the Holy Roman Emperor.