The rulers of Lorraine have held different posts under different governments over different regions. The first rulers of the region were kings of the Franks whose kingdom was called Lotharingia. The Latin construction "Lotharingia" evolved over time into "Lorraine" in French, "Lotharingen" in Dutch and "Lothringen" in German. After the Carolingian kingdom was absorbed into its neighbouring realms in the late ninth century, dukes were appointed over the territory. In the mid-tenth century, the duchy was divided into Lower Lorraine and Upper Lorraine, the first evolving into the historical Low Countries, the second became known as the Duchy of Lorraine and existed well into the modern era.
Charles the Bald claimed Lotharingia on Lothair's death and was crowned king in Metz, but his brother Louis the German opposed his claim and in 870 the Treaty of Mersen divided Lotharingia between the two brothers and subsequently their sons. In 880, the Treaty of Ribemont gave the whole of Lotharingia to Louis the Younger, son of Louis the German.
The Duchy of Lower Lorraine or Lower Lotharingia (also referred to sometimes as Lothier or Lottier in titles), established in 959 was a stem duchy of the medieval Kingdom of Germany, which encompassed almost all of the modern-day Netherlands (including Friesland), mid and eastern Belgium, Luxemburg, the northern part of the German Rhineland province and the eastern parts of France's Nord Pas De Calais region.
It was created out of the former Middle Frankish realm of Lotharingia under King Lothair II, that had been established in 855. Lotharingia was divided for much of the later ninth century, reunited under Louis the Younger by the 880 Treaty of Ribemont and upon the death of East Frankish king Louis the Child in 911 it joined West Francia under King Charles the Simple. It then formed a duchy in its own right, and about 925 Duke Gilbert declared homage to the German king Henry the Fowler, an act which King Rudolph of France was helpless to revert. From that time on Lotharingia (or Lorraine) remained a German stem duchy, the border with France did not change throughout the Middle Ages.