My great grandparents and all their children came from Castlecomer, Kilkenny, to the US in the 1860s. In Ireland they lived on Wandesforde property which covered many townlands and the coal mines in the area. The Topographical Dictionary of 1837 by Lewis has detailed information and is
found in most genealogy libraries and family history centers. My family lived on both Skehana and Firoda townlands northwest of Castlecomer and I believe there were Brennans found on one or both. If you like I could look up my research for the Tithe Applotment and Griffiths Valuation
and send you what I have in my notes. Good luck.