I did a quick check of both Irish censuses (1901 &1911) and the few Gildays are in Antrim and Leitrim so north would be right. The name struck a chord with me and I also remembered that there is a Father Francis Gilday Street in the South End of Boston. It's the original location of Boston College.

You might also what to look to see if there is a Gilday list. The Irish censuses for 1901 and 1911 are available free at the Irish National Archives site:

http://www.census.nationalarchives.ie/