MacNulty, Mac an Ultaigh, MacDuinnshléibhe, Dunleavy A Gaelic surname meaning ‘son of the Ulidian’ (East Ulster). The MacDuinnshléibhe sept of Donegal were also known as Mac an Ultaigh. In Meath the surname was Nulty. In 1890 McNulty was principally found in Donegal and Mayo, and the estimated number of bearers was 3,090. In the United States McNulty is the 2,847th most numerous surname with an estimated 11,000 bearers.