This week’s Irish Vocabulary lesson (see menu, above) includes Names of people and places that appear in Irish Firebrands.
In general, most ethnic Irish surnames are patronymic. There also are Gaelicized names that were assimilated from other peoples who settled in Ireland, such as Scandinavians, Anglo-Normans, and Anglo-Saxons. But the spellings and interpretations of many of these names can be debated.
Likewise, nobody knows for sure what was the original purpose of the earthworks on the Hill of Tara (I have my own theory, which I hope to use in a future novel).