Complex sentence: The claim that the Irish Gaels came from the Iberian region of Galicia may be based on the similarity of the names "Iberia" and "Hibernia" and the names "Galicia" and "Gael".
Split into simpler sentences: The claim that the Irish Gaels came from the Iberian region of Galicia may be based on three things. The first is the similarity of the names "Iberia" and "Hibernia" and the names "Galicia" and "Gael".