[1] The name derives from the Irish word scannal, originally meaning quarrel, contention, fight, or dispute.
One sept is O'Scannlain of Munster and the other is MacScannlain of Oriel, County Louth, neither of which has retained the prefix O or Mac in modern times.
The widespread distribution of these names is indicated by the fact that there are six Ballyscanlans in Ireland as well as a Scanlansland and a Scanlan's Island.
By tradition the dynasty was founded by Conall Corc but named after his ancestor Éogan, the firstborn son of the semi-mythological 3rd-century king Ailill Aulom.
[16] The rule of the Eóganachta in Munster is widely regarded as gentle and more sophisticated in comparison with the other provincial dynasties of Ireland.