The modern Shields family had its origin in the antiquity of the Emerald Isles
many generations before the existence of William Shields. The surname is an
Anglicized version of Siadhail, a family that was transplanted from the
European mainland perhaps as early as 1000 years before Christ. Members of the
Siadhail sept went northward from Meath into Ulster relatively late in Irish
History. The family presence in the Ulster area is evident before the Norman
Conquest of 1066.
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Reference:
Misty Spinelli
"Kin of my Grandchildren, Vol III", Judge Noble K. Littell, 1992, p 3, 7.
"Shields Family", Christine B. Brown, 6 February 1980, p 39.