Hello, Newt. That is a terrific surname you have there! My Corcoran line traces to Crissard townland, Rathaspick Civil Parish, County Laois, Ireland. My great-grandfather William Corcoran was my male line immigrant who landed in NYC in 1850, eventually settling in Clinton County in upstate New York. My siblings and I all still live in New York State. Two of William's sisters (Margaret and Frances) also emigrated to New York during the Famine, but all three emigrated in different years.
Unfortunately, it doesn't appear that your Corcoran line and my Corcoran line intersect. Perhaps way back we have someone in common. A Y-DNA test on your part would allow for a comparison of our two Corcoran lines, in addition to all other Corcorans who have taken that test. There are various factors to consider before deciding to take a Y-DNA test, however. It might be worth your time to read up a bit on Y-DNA testing and then decide whether it's for you.
As for your research, you may have gone back as far as you can go in Ireland. Civil record-keeping of births, marriages and deaths in Ireland didn't begin until 1849 for non-Catholics and 1864 for Catholics. Church baptism and marriage records can take you back a few decades earlier, but rarely do records of the Catholic Church peer back before 1800ish. A common starting point for Catholic Church record-keeping was around 1820. It can vary by Diocese.
You may be able to find a Tithe Applotment Land Record for Michael from the mid-1820s and other Corcorans in your line from the 1850s/1860s in Griffith's Valuation Land Records. Still, neither of these resources will take you back before 1820.
Best of luck!
