The name O'Grady originated from one of the most illustrious of the Dalcassian clans and one which has remained closely associated with County Clare. The surname is derived from the Irish form Ó Grádaigh or Ó Gráda (noble) and is said to come from their traditional ancestor, Grádach.

The present head of the clan, The O'Grady, or "chief of the name" as he is so styled, holds one of the few authentic native titles recognised by the State. The O'Grady family tree contains many other distinguished figures prominent in public and social life as well as members who became involved in cultural activities in times past.

The original territory of the O'Grady comprised much of the Barony of Lower Tulla, but an ancestor Hugh O'Grady left Clare in the beginning of the 14thcentury to settle at Killballyowen near Bruff in Co. Limerick where he acquired by marriage a good deal of land and property. His son William married a daughter of the Knight of Glin while the family continued to enjoy a high social standing, references to which may be found in Burke's "Landed Gentry of Ireland".

The most distinguished bearer of the name must be the scholarly Standish Hayes O'Grady who in his student days was a friend of both O'Donovan and O'Curry and undertook the task of cataloguing Irish Manuscripts in the British Museum.

His most important work, and of interest to local historians, is his translation of the "Caithréim Thoirdhealbhaigh" as recorded by Sean MacCraith, the only contemporary account of the principal events which occurred in North Munster from the 12th to the 14th century.

His cousin, Standish James O'Grady also gained a place in literature as novelist and historian. He wrote a history of Ireland emphasising the importance of our heroic period and widely known mythological figures. Several historical novels also came from his pen which include "In the Wake of King James", "The Flight of the Eagle" and "Red Hugh's Captivity" all of which aroused a new interest among his contemporaries in Irish epic literature.

The name is still to be found throughout East Clare while it is to Iniscealtra (Holy Island) in Lough Derg one must go to view an impressive memorial to their forebears complete with a carving of the family arms and motto "Vulneratus non Victur" - "Wounded not Conquered". It is erected in the interior of St. Caimin's Church whose splendid Romanesque Doorway is now fully restored; this tablet bears the following inscription "J. A. Grady reported those churches and monuments to the Grace and Glory of God 1703."

And another account:

The O'Grady sept originated in County Clare and may be classed as Dalcassian, though the seat and territory of the Chief of the name has for several centuries been at Killballyowen, County Limerick. The present holder of that dignity (i.e. in popular parlance "The O'Grady" is one of the very few the authenticity of whose claim to chieftainship is officially recognized in Ireland. The name in Irish is O'Grádaigh or more shortly O Gráda, so that the anglicized form approximates closely to the original. A peculiarity about it is that its leading family in County Clare, who favoured the English invaders in the time of Henry VIII, gradually changed their name from O'Grady to Brady, being described in legal documents of the sixteenth century as "O'Grady alias Brady" or vice versa. Thus the Bradys around Tuamgraney in East Clare are really O'Gradys, though Brady itself a common name in Ireland (especially in north Leinster and south Ulster) having no affinity with O'Grady at all. The ancestor of the present chief, though known at the time of his migration to County Limerick as John O'Grady alias Brady, dropped the latter and his descendants have ever since used teh ancient and correct form of their name. If we examine the distribution of the name in modern times we find that, combining the separate returns for O'Grady and Grady (which are of course the same name), the total is not inconsiderable amounting to some four thousand all told. The majority of these hail from County Clare as might be expected. This is followed by Mayo which is of interest because it has been stated, on what authority I cannot say, that there was a distinct O'Grady sept originating in Mayo - more probably it was an offshoot of the Dalcassian stock.

Many of the Gradys of Mayo and Roscommon are Greadys - Mag Riada in Irish, corrupted in the spoken language to O Griada. In County Tipperary Grady is often Gready in disguise, the Irish form there being O Greada. This, no doubt, is the original of the name Gredy and Graddy wich were regarded as numerous in the barony of Middlethird (County Tipperary) in 1659. There is a constant tendency for uncommon names to be assimilated to better known ones of a similar sound: thus Gready tends to become Grady, as does Graddy in Kerry.

John O'Grady was Archbishop of Tuam from 1364 to 1372. In modern times several members of the County Limerick O'Gradys have distinguished themselves in the service of Britain, one Standish O'Grady (1768-1840) being created Viscount Guillamore. The forename Standish with O'Grady is perpetuated by Standish Hayes O'Grady (1832-1915), who has been called "the last of the grand old scholars of Ireland".