O'Dea
O'Dea, is an Irish surname derived from Deághaidh, the name of a tenth-century clan chieftain. 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.
O'Dea clan origins
The O'Dea clan, also found as O'Day, Dea, or Day, came originally from County Clare in Ireland where there is a fortified tower house over 500 years old known as O'Dea Castle at the townland of Dysert O'Dea. The ruins of the Dysert O'Dea Monastery, round tower, and St. Tola's high cross are 265 metres to the south-southwest of the castle in the adjacent townland of Mollaneen, near Corofin.Edward MacLysaght, the former Chief Herald of Ireland, writing in his book, Irish Families, began his discussion of the O'Dea family as follows:
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."