The island's name is an anglicisation of the Gaelic Innis Mheàrnaig meaning Island of Marnock. Marnock, (Old Irish M'Ernóc, 'My [i.e. 'Saint'] Little Ernán) was a holy man who lived on the island in the 7th century and established a monastery. Alternatively, the name may simply be a dedication to Ernán and reflect the patron saint the monks on the island followed. He has also lent his name to a number of other locations:
