Docherty is an anglicized form of the Olde Gaelic name O'Dochartaigh, the Gaelic prefix "O" indicates "male descendant (of)", plus the personal name Dochartaigh, from "dochartach" meaning "hurtful" or "obstructive". The leading sept of the O'Dohertys (the usual anglicization of the name) belonged to Co. Donegal where they became Lords of Irishowen in the 14th Century.
The earliest recording of the surname in Ireland was in 1208, the year which David O'Doherty, a chief of Cinel Conaill was killed. There is an earlier recording of the name in the Isle of Man.
Today, the name Doherty with its variant forms Docherty, Docharty, Dougherty, etc., numbers fifteenth in the list of the most widespread names in Ireland. Sir Cahir O' Dougherty (1587 - 1608), lord of Inishowen who was knighted on the field of Augher.
The first recorded spelling of the family name is shown to be that of Donnall O' Dochartaigh, which was dated 1119, in the "Manx Names" by A.W.Moore, during the reign of the High Kings of Ireland "with opposition" 1022 - 1166. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.