Ivernic is an extinct Brythoniclanguage that was spoken in Ireland, particularly in Munster. It was spoken by a Gallo-Belgic tribe called the Érainn (in Irish) or Iverni (in Latin). They have been linked with the Fir Bolg (in the Irish Book of Invasions). Ptolemy's map shows a presence of Brigantes, a tribal name also found in Britain, in the south-east of Ireland. This language first diverged from Gaulish around 500 BC and survived the Gaelic invasion of Ireland (sometime between 500 and 100 BC). It was still spoken by a minority people in Munster at the time of Bede in about AD 700. However, its speakers eventually interbred with the Gaels and by the time the Vikings had established Limerick in about 850, the Ivernic language was extinct and completely replaced with Irish Gaelic.
Before Gaelic dialects evolved in Ireland, some allege that the inhabitants spoke Ivernic, particularly in Munster.
Cormac mac Cuilennáin, king and bishop of Cashel in Munster in Ireland, born 836, died 908, wrote a large Glossary which said that the "Iron-speech" was "dense and difficult" and had recently died out and that two words of it were remembered: ond = "stone" and fern = "anything good".
It is difficult to argue from two words, but it could be that Ivernic was language which was spoken in Ireland before any Indo-European languages arrived.