Following the Anglo-Norman invasion of Connachta rebellion in early 1200s the dynasty and related clans were expelled into Iar Connacht; their leader at the time was Aed Ua Flaithbertaigh, who died in 1236. They remained the area's rulers until the 1650s, when much of their lands were confiscated by the English Commonwealth. However, bearers of the name are still to be found in great numbers here and in other parts of County Galway. Three members of the family have served as Mayor of Galway in recent decades.
O'Flaherty is the anglicized version of the Gaelic Ó Flaithbheartaigh, which is commonly translated as "bright ruler". The clan motto is Fortuna Favet Fortibus, or "Fortune Favors the Bold". There are many incarnations of the name, including Flaherty, Fleharty, Fluharty, Flaverty, Faherty, Feherty, Fairty, Laverty, and Lafferty. The O'Flahertys were war-like, as evidenced by the sign which is said to have hung over the west gate of the city of Galway: "from the ferocious O'Flahertys may God protect us". Unlike their merchant neighbours in this Anglo-Norman city, the O'Flahertys kept the Brehon Laws, in which The O'Flaherty, the clan leader or taoiseach was chosen from among the extended family of the clan chief as opposed to his eldest son, as would be the case in English Law. The O'Flahertys controlled their lands from a series of castles, the largest of which, Aughnanure, near Oughterard, is open to the public today.