Moriarty is the English version of the Irish O Muircheartaigh, made up of muir, "sea", and ceardach, "skilled", "one skilled in the ways of the sea". The name is undoubtedly linked to their original homeland, on both sides of Castlemaine harbour in south Co. Kerry. The continuity of their association with the area is remarkable, even by Irish standards. They have lived in the area since the surname came into being in the eleventh century, and ninety per cent of present births of the surname are still in Co. Kerry. This continuity is all the more tenacious for the fact that they had lost virtually all of their power in the area by the fourteenth century. O Muircheartaigh was also a surname found in Meath and the midlands, but in these areas it has been anglicised as "Murtagh". Murtagh is also the anglicisation commonly found in Ulster for O Muircheartaigh, though it has also been given as Murdoch, by association with the common Scottish name.
The presence of the original O Muircheartaigh in the north is reflected in placenames, with Killymoriarty in Co. Armagh and Kilmoriarty in Co. Cavan.
The famous American preacher and temperance reformer Patrick Moriarty (1804-1875) was born in Dublin of a Kerry family..
David Moriarty (1814-1877) was a Catholic bishop of Kerry notorious for his vehement denunciations of all opposition to the British government, saying of the Fenian leaders "eternity is not long enough nor Hell hot enough for such miscreants."
Micheal O Muircheartaigh is one of the best-known sports broadcasters in Ireland. His distinctive Kerry tones are an essential feature of All-Ireland finals.
Professor Moriarty was Shelock Holmes? fiendishly clever arch-opponent.