The O'Doherty name is primarily associated with Co. Donegal. The family can trace back its origins to the parish of Kilteevoge but Inishowen is now considered the homeland of the clan. They descend from the same line as the O'Donnells. It was the most numerous name in Donegal in the census of 1659, spelled as O'Dogherty(e) at that time, but it’s Gaelic spelling is unequivocal as Ó Dochartaigh, generally thought to derive from the nickname of a chieftain called An Dochartach, meaning The Destroyer, who flourished during the early decades of the 9th-century. His real name was Donnchadh and his family group was known as Clann Fíamhain but the surname – one of the first to be used in Ireland – took its form from An Dochartach’s grandson who was known as Ó Dochartaigh, translating as Grandson of the Destroyer.
Their main territory was a fortress high up on a hill outside the town of Stranorlar called Ard Miodhrain (now written Ardmiran) overlooking the Finn River. But they extended their lands and became Lords of the Inishowen peninsula in the 1400s.
The Normans had reconstructed the old fortification of Cúil Mhic Giolla Tréin (later re-named Castleforward) on the Swilly, south of Inishowen. By 1333 they had vacated Castleforward and Inishowen and the political vacuum was filled shortly afterwards by the Ó Dochartaigh clan of Ard Miodhair. Gradually all the old castles of Inishowen were occupied by the new Gaelic Ó Dochartaigh lords who also had new ones built.
Dozens of castle sites have been identified as residences of the clan.
They remained as chiefs of Inishowen down to the reign of James I, when the 20-year- old Sir Cahir O'Dogherty was killed in a battle with the English in 1608. The McDevitts and McDaids of the same areas are an offshoot of this family, descending from David O'Doherty, a chief of the name in the 13th century.
Many O'Dohertys today use the name without the “O” prefix as a result of malpractices of British civil administrators over the last four centuries who showed scant regard for correct spellings. By 1890 only 7 O'Doherty births were recorded in Ireland, while the Doherty name itself proliferated. Modern-day residents continue to reverse this trend by adding the “O” back onto the name and a smaller number of the clan who speak and write the Irish language prefer to use the original Ó Dochartaigh