thumb|upright=1.25|The Iverni ("Iwernoi" above) are one of the population groups mentioned in [[Ptolemy's Geography.]]
The Iverni (, ') were a people of early Ireland, first mentioned in Ptolemy's 2nd century Geography as living in the far south-west of the island. He also names a "city" called Ivernis (, ') in their territory, and observes that this settlement has the same name as the island as a whole, Ivernia (, '). These Iverni are identified with the Érainn (Érnai, Érna), a people attested in Munster and elsewhere in the early Middle Ages. They included the Corcu Loígde, Corcu Duibne, Corcu Baiscind, Múscraige and Déisi, as well as the Dál Fiatach and Dál Riata. Their royal dynasties are sometimes referred to as the Dáirine.
Name
The name 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 full, fat, fertile land) – cognate with the Ancient Greek píeira and Sanskrit pīvara, which refer to fertile land. In his 2nd century Geographia (), Ptolemy called the island Iouernia or Iwernia (; ou represented /w/) and named a tribal group called the Iouernoi or Iwernoi () in the southwest.
The people of Ireland are called the in the 3rd century Panegyric on Constantius Caesar, written in 297 AD.
In the Ora Maritima, Roman writer Avienius says that Ireland is inhabited by the (the Hierni people, or the Irish). Though the text dates to the 4th century AD, he was using much older sources, and this part is widely agreed to be based on the Massaliote Periplus from the 4th–6th century BC.
In the 5th–6th century AD, Saint Patrick referred to the Irish as the , (genitive plural ). In early Irish genealogical tracts, the Érainn are regarded as an ethnic group, distinct from the Laigin and Cruthin.
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. Another prominent Érainn people of early Munster are believed to have been the Mairtine, who by the early historical period have vanished from the Irish landscape, although they may be in part ancestral to the later Déisi Tuisceart and Dál gCais.
The historical sept of the Uí Maicc Iair ("grandsons of the son of Iar") and the <small>MAQI IARI</small> of ogham inscriptions also appear to be related. The personal name Iar is simply another variant of the root present in Iverni and Érainn. Finally, the name Íth, given in the genealogies as the ultimate ancestor of the Corcu Loígde (Dáirine) also preserves the same root as Iverni/Érainn, thus completing a basic picture of the Iverni/Érainn and their kindred in later historical Ireland.
Darini, Dáirine
It seems likely the Iverni/Érainn were related to Ptolemy's Darini of eastern Ulster, later called the Dáirine. The name "Dáirine" implies descent from an ancestor called Dáire (*Dārios), as well as the Érainn of Munster. An early name for Dundrum, County Down, is recorded as Dún Droma Dáirine, and the name Dáirine was applied to the Corcu Loígde, further suggesting a relationship between the Dáirine and the Érainn. actually meant "Ivernic/Érainn language", and that this unattested language was spoken until the 7th century AD.
His theory has been rejected by later linguists, archaeologists and historians. There is no archaeological or genetic evidence of large migrations to Ireland after the Bronze Age. Evidence shows that the Iverni and the Érainn were Gaelic-speaking from the beginning of recorded history. The oldest surviving examples of Gaelic are ogham inscriptions in Archaic Irish – most of these are in Érainn territory in the southwest.