Ireland was settled, like the rest of northern Europe, after the retreat of the ice sheets c. 10,500 BC.
Some scholars hypothesize that the Goidelic languages may have been brought by the Bell Beaker culture circa 2500 BC.
This dating is supported by DNA analysis indicating large-scale Indo-European migration to Britain about that time.
[2] In contrast, other scholars argue for a much later date of arrival of Goidelic languages to Ireland based on linguistic evidence.
Peter Schrijver has suggested that Irish was perhaps preceded by an earlier wave of Celtic-speaking colonists (based on population names attested in Ptolemy's Geography) who were displaced by a later wave of proto-Irish speakers only in the 1st century AD, following a migration in the wake of the Roman conquest of Britain, with Irish and British Celtic languages only branching off from a common Insular Celtic language around that time.