The Clan/Sept History

Barrett is a well known Irish clan which includes various septs including MacPadine, MacWattin, MacEvilly (Mac an Mhileadha), and MacAndrew. There are two Barrett clans in Ireland which were believed to be unrelated before recent research proved otherwise. They are Norman in origin, and trace their ancestry to a John Baret who came over from France with William the Conquerer and are mentioned in the Domesday book. The Barretts then came to Ireland with the Norman warlord Strongbow (Richard Le Clare, the Duke of Pembroke) at the end of the twelfth century.
The first branch of the clan are the Munster Barretts of Co. Cork, and the other is the Barrett clan of Connacht, most numerous in the Mayo-Galway mountain region. This clan was thought to be Gaelic in origin, although it known that they came to Ireland with the Norman invasion. They were hired mercenaries from Wales. To this day, the Barretts and the Barrys of Connacht are known as "the Welshmen of Tirawley".
The similarity of the names of the two Barrett clans was thought purely coincidental. The view prevailed that the Barretts of Cork derived their name from the Norman-French "Barratt," while the Barretts of Connacht derived their name from the gaelic name "Bairéad" which means quarrelsome or warlike . In fact, many daughters and sons of the clan, living in Connacht, are still called Bairéad (or mac Bairéad, as the case may be). But the English pipe rolls of the 13th century clearly indicate that the overlords of both the Cork and the Mayo Barretts were exactly the same people, and the records further indicate that both families came from Pendyne in Wales.
Both branchs of the Barrett clans were fully assimilated into Irish culture and married into many old Irish families, they are said to have become "more Irish than the Irish themselves".
You will find many Barretts/Bairéads in Irish history serving the Irish nation such as Col. John Barrett who raised a regiment of infantry for King James' army in Ireland, afterwards he and his clan suffered a wrath of genocide and land confiscations dealt by the Williamite armies in 1691. There was Ríocard Bairéad "The poet of Erris", a prominent United Irishman; to name a few.