Tully, Mac Maoltuile, ó Maoltuile A Gaelic surname meaning descendant of Maoltuile (devoted to the will, i.e. of God). A sept of Roscommon who were hereditary physicians to the O’Connors of Connacht and the O’Rourkes of Breifney. This has been shortened to MacTuile, and also corrupted to Mac an Tuile. Also translated as Flood, owing to tuile being ‘flood’. In 1890 the surname was principally found in Galway, Dublin and Cavan, and the estimated number of bearers was 2,020. In the United States Tully is the 5,176th most numerous surname with an estimated 5,500 bearers.