Prepared by Elisabeth Lindsay.
Irish surnames have undergone many transformations over time. The Irish were known by their Gaelic Clan or tribe names, which were often centralized within a given area. Many Irish surnames were created by adding prefixes to individual names. The prefix "Mac" or its abbreviated "Mc" indicated the "son of"; whereas "O" indicated the "grandson of," resulting in names such as McDonald and O'Malley. With the English invasion, as a means of survival, Gaelic names were commonly Anglicized, resulting in many variations, some barely resembling the original name. Over time, many Irish went back to their Gaelic roots and reclaimed their clan surnames.
One of the most important aspects of Irish research is understanding the history of the land and its effect on surnames. Knowing how a surname changed and when, is important, especially Anglicized versions of Irish surnames. Also important is knowing the region with which a particular clan is associated, even though people did migrate out of their clans. According to one source, "the 'Scottish Gaels' were actually descendants of Gaelic emigrants to Scotland. The word 'Scotus' is Latin for "Irishman." Scottish settlers who moved to Ireland (and especially Ulster) may already have been of Gaelic Irish descent." A number of resources on the Internet are available to aid in researching Irish surnames. One source, Irish Clans and Surnames, identifies the surnames associated with a particular locale, along with a list of Irish Clan web sites which can provide further information.