O'Dea/O'Day/Dee (DNA) Project

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About us

Welcome to the home page of the O'Dea/O'Day/Dee (DNA) Project.
The Irish surname O'Dea, or in Irish Ó Deaghaidh or Ó Deághaidh or Ó Deá, is, according to MacLysaght, that of one of the principal Dalcassian septs, common in Thomond (now County Clare). Seán de Bhulbh writes that there were septs in Clare and Tipperary.
Away from its homeland, where it is often pronounced "O'Day", the surname is usually pronounced as "O'Dee", leading to potential confusion with Ó Diaghaidh, which is a distinct name. MacLysaght notes that, as Dia is the Irish word for God, this accounts for the use of Godwin in County Mayo as a synonym.
The O' prefix is now almost always used, but in the 19th century Dea was quite usual and the English Day (which has a separate FTDNA project) was regarded as synonymous. Another occasional synonym is Daw.
The name has since spread throughout Ireland and abroad. The 1911 census of Ireland included 1,318 O'Deas, just over half of them (679) born in County Clare.
This DNA project is being operated in conjunction with the Dysert O'Dea Clan Association, which organises annual gatherings in Ireland, including in May 2018. For more details, see the association's website.
The project administrators are James O Dea of the Dysert O'Dea Clan Association and genetic genealogist Paddy Waldron (GGGGgrandson of an O'Dea). Paddy Waldron's personal website has a great deal of useful additional reading on genetic genealogy, such as How to get the most out of your DNA results and Interpreting Y-DNA results.
  1. If you are not already a project member and you have any ancestor with the surname O'Dea (or a variant spelling), then please JOIN the project by clicking on the JOIN button to the right of the shopfront in the banner photograph above.
  2. To benefit from project membership, it is imperative that you squeeze in names, dates and places to the 50 characters allowed for both your Direct Maternal (i.e. matrilineal) and Direct Paternal (i.e. patrilineal) Most Distant (i.e. most distant known) Ancestors here in order to help those looking for mitochondrial DNA matches and Y-DNA matches respectively; and that you also upload a GEDCOM file here showing your direct ancestors (which will automatically populate your surname list).
  3. For a discussion of the latest results, see here.
  4. Please feel free to use the Activity Feed to direct any questions that you may have to the project administrators and for discussion with other project members.