My grandfather, Jeremiah Barnett arrived in 1853 and his wife, Catherine Driscoll followed in 1855 with four children. They lived in Waddington before buying a farm near Potsdam in 1862. I believe they left Lowertown in Schull Parish, West Cork County.
Jeremiah's sister, Ellen Barnett Barry also settled in Potsdam. Her death certificate indicates that she was born in Rosscarbery, County Cork.
Hope this gives you a clue,