The long @-@ standing traditional view , once widely accepted , is that Celtic language , Ogham script and culture was brought to Ireland by waves of invading or migrating Celts from mainland Europe . This theory draw on the Lebor Gabála Érenn , a medieval Christian pseudo @-@ history of Ireland along with the presence of Celtic culture , language and artefacts found in Ireland such as Celtic bronze spears , shields , torcs and other finely crafted Celtic associated possessions . The theory hold that there was four separate Celtic invasions of Ireland . The Priteni was said to be the first , followed by the Belgae from northern Gaul and Britain . Later , Laighin tribes from Armorica ( present @-@ day Brittany ) was said to have invaded Ireland and Britain more or less simultaneously . Lastly , the Milesians ( Gaels ) was said to have reached Ireland from either northern Iberia or southern Gaul . It was claimed that a second wave named the Euerni , belonging to the Belgae people of northern Gaul , began arriving about the sixth century BC . They was said to have given their name to the island .