The Iverni (, ) were a people of early Ireland first mentioned in Ptolemy's 2nd century Geography as living in the extreme south-west of the island. He also locates a "city" called Ivernis (, ) in their territory, and observes that this settlement has the same name as the island as a whole, Ivernia (, ). It was probably once the name given to all the peoples of Ireland, but by Ptolemy's time had a more restricted usage applicable to the inhabitants of the south-west. These Iverni can be identified linguistically with the Érainn (Éraind, Érnai, Érna), a people attested in Munster and elsewhere in the early Middle Ages. The prehistoric Érainn royal dynasties are sometimes referred to as the Dáirine. Etymology The name Iverni has been derived from Archaic Irish *Īwernī meaning "folk of *Īweriū " (the island of Ireland). This is in turn derived from Proto-Celtic *Φīwerjon- and further from Proto-Indo-European *piHwerjon- (the fertile land), which is cognate with the Ancient Greek píeira and Sanskrit pīvarī, which refer to fertile land. John T. Koch writes it was probably once the name given to all the peoples of Ireland, but by Ptolemy's time had a more restricted usage applicable to the inhabitants of the south-west. Historical septs In early Irish genealogical tracts the Érainn are regarded as an ethnic group, distinct from the Laigin and Cruthin. Population groups in Munster classed as Érainn include the Corcu Loígde in southwest County Cork, the Múscraige in Counties Cork and Tipperary, the Corcu Duibne in County Kerry, and the Corcu Baiscinn in west County Clare. The Dál Riata and Dál Fiatach (or Ulaid) in Ulster are also considered Érainn. The Érainn appear to have been a powerful group in the proto-historic period, but in early historical times were largely reduced to politically marginal status, with the notable exception of the enigmatic Osraige. The most important of the Munster Érainn, the Corcu Loígde, retained some measure of prestige even after they had become marginalised by the Eóganachta in the 7th or 8th century. It is likely that the sometimes powerful Uí Liatháin and their close kin the Uí Fidgenti originally belonged to the Érainn/Dáirine as well, but were later counted among the Eóganachta for political reasons. Another prominent Érainn people of early Munster are believed to have been the Mairtine, who by the early historical period have completely vanished from the Irish landscape,