In the ninth century, Vikings settled the Cotentin, which became part of Normandy in the early tenth century. Many place names there come from the Norse language. Examples include La Hague, and La-Hougue both derived from the Old Norse word "haugr" meaning a hill or mound. Until the construction of modern roads, the peninsula was almost inaccessible in winter because of marshland cutting off the higher ground. This explains occasional historical references to the Cotentin as an island.