O'Dea (/oʊˈdiː/oh-DEE; Irish: Ó Deághaidh, formerly Ua Deághaidh), is an Irish surname derived from Deághaidh, the name of a tenth-century clan chieftain.[1] According to historian C. Thomas Cairney, the O'Deas were one of the chiefly families of the Dal gCais or Dalcassians who were a tribe of the Erainn who were the second wave of Celts to settle in Ireland between about 500 and 100 BC.[2]
O'Dea is a name associated alike in the past and at present almost exclusively with the County Clare and the areas such as Limerick City and North Tipperary which immediately adjoin it. It is not a common name anywhere and even in County Clare is not numerous outside the part of the county where it originated. This is indicated by the place names Tully O'Dea and Dysart O'Dea, the site of a famous battle in 1318. The head of the sept was chief of a considerable territory comprising much of the barony of Inchiquin. In Irish the name is Ó Deághaidh.[7]
In another book, The Surnames of Ireland, MacLysaght describes the O'Deas as "one of the principal Dalcassian septs", and about the name itself, he remarks, "The prefix O is now almost always used, but a century ago Dea was quite usual and the surname Day was regarded as synonymous."[8]
Ancestry
The O'Deas – together with the O'Quinns (Irish: Ó Cuinn) and the O'Griffins (Irish: Ó Gríofa) – belonged to the Uí Fearmaic group, which was a branch of the Dalcassian tribe.[9]
^Dysart O'Dea Castle, Co. Clare by Risteard Ua Croinin and Martin Breen, The Other Clare, Volume 9, page 17. Shannon Archaeological and Historical Society, April 1985.
^Irish Families: Their Names, Arms and Origins, by Edward MacLysaght. Dublin: Hodges Figgis 1957, rev. 1972, page 112.
^Surnames of Ireland, by Edward MacLysaght. Shannon: Irish UP 1969.
^O'Laughlin, Michael C. (21 March 2024). Families of County Clare Ireland. Irish Genealogical Foundation. ISBN978-0940134980.
Further reading
O'Dea: Ua Deághaidh: The Story of a Rebel Clan, by Risteárd Ua Cróinín (Richard Cronin), Ballinakella Press, Whitegate, Co. Clare, Ireland, 1992. ISBN0-946538-07-7.
Irish Battles – A Military History of Ireland, by G.A. Hayes-McCoy, Appletree Press, 1990, ISBN0-86281-250-X