Mac Íosóc
Mac ÍOSÓC, Mac ÍOSÓG—V—M'Isock, M'Kysoke, M'Kyssock, M'Kysog, MacKissock, MacCussack, Kissack, Cusack; 'son of Isaac'; the name of an old Thomond family; found also in Galway, Roscommon and Donegal. It was also an old surname in the Isle of Man, where it is still represented by Kissack.
Alphabetical Index to Irish Surnames