When Isaac McMunn was born on 24 March 1809, in Pittsburgh, Allegheny, Pennsylvania, United States, his father, Alexander McMunn III, was 56 and his mother, Elizabeth, was 40. He married Maria Moore on 18 April 1833, in Jefferson, Ohio, United States. They were the parents of at least 6 sons and 5 daughters. He lived in Olive Township, Morgan, Ohio, United States in 1850 and Ohio, United States in 1870. He died in 1874, in Sharon Township, Noble, Ohio, United States, at the age of 65, and was buried in Sharon Township, Noble, Ohio, United States.
Scottish and Irish: shortened Anglicized form of Gaelic Mac Gille Munna (McIlMunn) ‘son of the servant (or devotee) of (Saint) Munnu’, Munnu being a pet name for Saint Fintan of Taghmon. This name, which is also found in the form Mundu, from earlier Mo-Fhindu, is a hypocoristic form of Fionntan with the affective prefix mo- ‘my’. Although Fintan was an Irish saint, this surname appears to have been coined in Scotland, where there was a place called Kilmun ‘Saint Munnu's church’, near Inverary.