ancestry.com suggested this link, and it is interesting:
This is 1838, parish of Kilkeevin, birth of "Pat Grady of Michalis (Grady) and B. Ganly"
We can thank the parish priest for the latinization of Michael to Michalis.
But 1838? When Patrick dies 1878 he is listed as 30 years old, which would make his birth 1848!
The Michael Grady (gr-gr-grandfather) and Ganly (gr-gr-grandmother) parts are too close to dismiss this, however. And Creggameen, where Ganlys are from, across from Derreentighe, is in Kilkeevin.
Interesting!