Irish: Anglicized form of Gaelic Mac Cárthaigh ‘son of Cárthach’ a personal name meaning ‘loving’. This was the name of a ruling family in Munster. In Ireland major branches were distinguished by the following epithets: mór ‘great’ in Kerry riabhach ‘brindled’ in Carbery west Cork.
Source: Dictionary of American Family Names 2nd edition, 2022