The Danes were a North Germanic tribe inhabiting southern Scandinavia, including the area now comprising Denmark proper, northern and eastern England, and the Scanian provinces of modern-day southern Sweden, during the Nordic Iron Age and the Viking Age. They founded what became the Kingdom of Denmark. The name of their realm is believed to mean "Danish March", viz. "the march of the Danes", in Old Norse, referring to their southern border zone between the Eider and Schlei rivers, known as the Danevirke. Dan (king) The origin of the Danes remains undetermined, but several ancient historical documents and texts refer to them and archaeology has revealed and continues to reveal insights into their culture, cultural beliefs, beliefs organization and way of life. The Danes first appear in written history in the 6th century with references in Jordanes' Getica (551 AD), by Procopius, and by Gregory of Tours. They spoke Old Norse (dǫnsk tunga), which the Danes shared with the people in Norway and Sweden and later in Iceland and the Faroe Islands. In his description of Scandza, Jordanes says that the Dani were of the same stock as the Suetidi ("Swedes") and expelled the Heruli and took their lands. The Old English poems Widsith and Beowulf, as well as works by later Scandinavian writers (notably by Saxo Grammaticus ( 1200)), provide some of the original written references to the Danes. According to the 12th-century author Sven Aggesen, the mythical King Dan gave his name to the Danes. The Danes spoke Proto-Norse which gradually evolved into the Old Norse language by the beginning of the Viking Age. Like previous and contemporary people of Scandinavia, the Danes used runes for writing, but did not write much apparently, as they have left no literary legacy except for occasional rune stones and carvings in wood and various items like weapons, utensils and jewellery. As previous and contemporary peoples of Scandinavia (the Vikings), the tribal Danes were practitioners of the Norse religion.