I have lived in Hanover for 26 years but was born and raised in Dorchester. My grandfather was from Ireland but as to where, that info has been debated for years. My mother was a Fennessey and her parents were from County Waterford. When I was a child, there was only one other un-related O'Hearn family in eastern Mass(O'Hearn Moving and Storage). The O'Hearn School in Dorchester was named after my grandfather.