The Ivernic reference article from the English Wikipedia on 24-Jul-2004
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Ivernic

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Ivernic is an extinct Brythonic language that was spoken in Ireland, particularly in Munster. It was spoken by a Gallo-Belgic tribe called the Érainn (in Irish), Iverni (in Latin), and Firbolg (in the Irish Book of Invasions). This language first diverged from Gaulish in 500 BCE and survived the Gaelic invasion of Ireland (sometime between 500 and 100 BCE). It was still spoken by a minority people in Munster at the time of Bede in about 700 CE. However, its speakers eventually interbred with the Gaels and by the time the Vikings had established Limerick in about 850 CE, the Ivernic language was extinct and completely replaced with Irish Gaelic.