O’Toole, ó Tuathail A Gaelic surname meaning descendant of Tuathal (meaning, people mighty). One of the principle septs of Leinster, originally of Kildare they moved to Wicklow. In 1890, the estimated number of persons bearing the surname was 4,500, and the surname was principally to be found in Dublin, Galway, Wicklow and Kildare. In the United States Toole is the 5,470th most numerous surname with an estimated 5,500 bearers.