Dermod O'Shaughnessy, son of William O'Shaughnessy, is a figure identified in the O'Shaughnessy clan's lineage, but he did not leave an extensive personal historical record as a major chief. Instead, he represents a crucial link in the chain of succession leading to the more famous Sir Dermot O'Shaughnessy of the Tudor and later periods.
There are two primary figures this relationship could reference, based on the documented genealogy of the Chiefs of Cinéal Áeda na h-Echtghe (Kinelea) in County Galway:
This individual is the most direct genealogical match for "Dermod, son of William" in the medieval O'Shaughnessy pedigree.
Role: An ancestor in the pre-16th-century line of Gaelic chiefs.
Paternity: He was the son of William O'Shaughnessy (son of John "Buidhe" O'Shaughnessy).
Succession: His son was named Giall-Dubh (or Gilla-Duv) O'Shaughnessy.
Significance: Like many intermediate figures in ancient Gaelic genealogies, he is known primarily for his place in the family tree, which traces the descent of the O'Shaughnessys from the 10th-century founder, Seachnasach mac Donnchadh, and ultimately back to the Uí Fiachrach Aidhne dynasty. He served to maintain the lineage during a period when the family solidified its power in South Galway.
The Dermod O'Shaughnessy, son of William, is best understood as a genealogical link who ensured the survival of the senior O'Shaughnessy line, which later produced the powerful chiefs who interacted with the Tudor and Stuart monarchs (like the Sir Dermot O'Shaughnessy knighted by Henry VIII).