MacCarthy MacCarthy MacCarthy (Irish: Mac Cárthaigh), also spelled Macarthy, McCarthy or McCarty, is a Gaelic Irish clan originating from Munster, an area they ruled during the Middle Ages. It was and continues to be divided into several great branches. The MacCarthy Reagh, MacCarthy of Muskerry, and MacCarthy of Duhallow dynasties were the three most important of these, after the central or MacCarthy Mór line. Their name, meaning "son of Cárthach" (whose name meant "loving"), is a common surname that originated in Ireland. As a surname, its prevalent spelling in the English language is McCarthy. Several variants are found, such as McCarty
Mac and Mc together in print two publications on filing rules, one covering that "word-by-word" convention, and another prepared in 1980 that is "letter-by-letter". A 1998 book attributes the changes to the rules to computer informatics, and notes the Mac/Mc change as its first example. 1982's "Scottish Roots", a guide for family history researchers, warns that older Scottish records do not in fact follow this convention, unlike contemporary telephone directories. A 2001 book of "New York Times" theatre reviews sorts Mc names as if spelled Mac. A 2002 official document for the State of Vermont recommends explicitly no special treatment for Mac and Mc.