Denison, Deniss
Denison, Deniss—In the districts of Cong, Co. Mayo, and Sligo the name McDonagh (Mac Donnchadh) has been anglicised Denison and Deniss. The McDonaghs were a branch off from the McDermotts of Moylurg, and ruled in Sligo.
Alphabetical Index of Anglicised Surnames in Ireland
See also Woulfe’s Irish Names and Surnames
… and O'Hart's Irish Pedigrees