Gaelic (Irish) is a Celtic language and, as such, is a member of the Indo-European family of languages. Within the Celtic group, it belongs to the Goidelic branch of insular Celtic. Irish has evolved from a form of Celtic which was introduced into Ireland at some period during the great Celtic migrations of antiquity between the end of the second millennium and the fourth century BC. Old Irish, Ireland’s vernacular when the historical period begins in the sixth century of our era, is the earliest variant of the Celtic languages, and indeed the earliest of European vernaculars north of the Alps, in which extensive writings are extant.The Norse settlements (AD 800 onwards) and the Anglo-Norman colonization (AD 1169 onwards) introduced periods of new language diversity into Ireland, but Irish remained dominant and other speech communities were gradually assimilated. In the early sixteenth century, almost all of the population was Irish-speaking. The main towns, however, prescribed English for the formal conduct of administrative and legal business.