Moriarty
An Irish surname usually understood as meaning “sea-ruler” or “sea-true,” from an old Gaelic personal name.
The #3,564 most common surname in the United States (2010 Census) — about 1 in every 30,859 Americans shares it.
Etymology
Moriarty comes from the Gaelic personal name Muircheartach, which is commonly explained as muir, “sea,” plus a form of ceart meaning “right,” “just,” or “true,” with the personal-name ending -ach. That gives the sense of someone who is “sea-right,” “sea-true,” or more loosely “sea-ruler.” Some older writers offered a different interpretation, but the sea-related explanation is the standard one in the sources here.
History
The name is well established in Ireland and is especially associated with County Kerry, where the O’Moriartys were recorded as local chiefs in the Barony of Dunkerron. In modern usage the O’ prefix has often been dropped, leaving Moriarty as the common surname form. It also appears in historical Irish surname lists and remains relatively concentrated in southwest Ireland and among Irish diaspora families.
Origin
Regions
Variant spellings
Fun fact
19th-century Irish surname studies place Moriarty among the better-known Kerry names, reflecting its long local prominence there.
From the historical record
“Morgan [ap, ab, son] MORIARTY (Celt.) Sea-Right or Sea-True [Ir. Muircheartach — muir, sea + the asp. form of ceart, right, justice, true -|- the pers. suff. -acK] Morice”
— Surnames of the United Kingdom: a concise etymological dictionary (2 vols in 1)Notable people named Moriarty
Sourced from Wikidata; linked to their Wikipedia page.