O'Toole is an Irish surname that represents the Anglicized form of the native Gaelic Ó Tuathail, meaning "descendant of Túathal". The root Túathal itself derives from Old Irish túath "people, country" and fal "rule", thus signifying "ruler of the people". This name was borne by several early Irish kings, including the legendary Túathal Techtmar, a high king said to have reigned in the 1st or 2nd century AD.The surname O'Toole is historically rooted in County Wicklow and County Kildare in Leinster, where the Ó Tuathail sept was a leading family of the Uí Máil tribal group. The O'Tooles were renowned for their resistance to Norman and later English incursions, with figures such as Art Óg Ó Tuathail being a noted Irish chieftain in the 14th century.A common variant of the surname is Toole, which omits the O' prefix. The original Gaelic form Ó Tuathail remains in use today, maintaining a direct link to the name's ancient heritage.