The name Agder was not used after 1662, when the area was split into smaller governmental units called Nedenæs, Råbyggelaget, Lister, and Mandal.

In the early Viking Age, before Harald Fairhair, Agðir was a petty kingdom inhabited by a people named after it, the Egðir.

The Egðir are believed to be the same etymologically as the Augandzi people mentioned in the Getica of Jordanes, who wrote of Scandza (Scandinavia) in the 6th century.

Norway of the Viking Age was divided into petty kingdoms ruled by chiefs who contended for land, maritime supremacy, or political ascendance and sought alliances or control through marriage with other royal families, either voluntary or forced.

The previous most credible source, Ptolemy, gives the briefest of sketches, only citing all of Norway as the Chaedini ("country people").

It seems clear that in the Roman Iron Age Norway was populated by people of the same identity as Sweden, who were called the Suiones by Latin sources.

After the unification of Norway by Harold Fairhair and army and allies in the 10th century, all the civitates became provinces (fylker) and after their conversion to Christianity, they became dioceses or parishes.

The development of Old Norse into local dialects and the dissimilation of customs due to isolation added an ethnic flavor to the area, which is cherished today.