This notable name, with variant spellings O'Grady, O'Grada and the rarer form Gready, is an Anglicized form of the Old Gaelic "O' Gradaigh". The Gaelic prefix "O" indicated "male descendant of", plus the personal byname "Gradaigh", from "grada", the illustrious one. This sept belonged to the Dal gCais (otherwise known as the Dalcassians), embracing the main septs of Thomond, an ancient territory comprising most of County Clare, with adjacent parts of Counties Limerick and Tipperary. The seat and territory of the Chief of the Name was at Killballyowen, County Limerick. It is interesting to note that "The O'Grady" is one of the few whose claim to chieftainship is officially recognised in Ireland. A branch of the family in East Clare, who supported the English invaders in the reign of Henry 111 (1216 - 1272), changed their name from O'Grady to Brady, whereas in parts of Counties Mayo and Roscommon some Gradys took the name Gready, itself from the Gaelic "Mac Riada", corrupted in the spoken language to O'Griada. The first recorded spelling of the family name is shown to be that of John O' Grady, Bishop of Tuam, which was dated 1364, in "Ecclesiastical Records of County Galway", during the reign of King Edward 111, known as "The Father of the Navy", 1327 - 1377. 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.