The O' Gara clan and the O' Hara clan have the same origin although after about the 15th century they went their own way.They originate from County Sligo before the 10th century a.d. descending from Eaghra, chief of Leyny, and a member of the household of Ollum, King of Munster. Later the clan was split into three septs, the chiefs of O' Gara being the barons of Costello in County Mayo, whilst O 'Hara branches were known as O' Hara Buide (the brown faced one) and O' Hara Reagh, the rough faced one! Both the O'Gara and O'Hara clans were ultimately large landlords in County Sligo, between them possessing an estimated 40,000 acres, the O' Gara's being to the south and in the barony of Leyney, County Sligo, with their castle at Ballygara on Lough Gara. Colonel Oliver O' Gara commanded the Irish Brigade in the army of France in the mid 18th century, whilst one of the first recorded millionaires was Charles O' Gara of Brussels, at the time of the French Revolution in 1792. Kean O'Hara was a participant with Lord Edward Fitzgerald in the 1798 Irish rebellion. Both escaped to France, where they served as officers in the armies of Napoleon Bonaparte. The first recorded spelling of the family name is shown to be that of Dermot O'hEaghra, which was dated circa 1350, in the "Composition book of Connacht", during the reign of King Edward 111, of England, 1327 - 1377. Surnames became necessary when governments introduced personal taxation. In England this was sometimes known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.