Ó Siadhail
Ó SIADHAIL, Ó SIAGHAIL—I—O Siegall, O Shiell, O Sheale, O Sheill, O Shill, O'Shiel, Sheil, Shiels, Sheils, Shields, Sheilds, Sheils, Shiles, Sheals, &c.; 'descendant of Siaghal' or 'Siadhal' (compare with siadhail, sloth); the name of a family of the race of Maine, son of Niall of the Nine Hostages, who became celebrated as physicians and surgeons in many parts of Ireland, as in Delvin-MacCoghlan, Oriel, Inishowen, &c. Owen O'Sheil, known as the 'Eagle of Doctors,' was physician to the armies of the Confederate Catholics of Ireland from 1642 to 1650.
Alphabetical Index to Irish Surnames