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The surname Mulcahy is of Irish Gaelic origin, being anglicised from "Ó Maolchathaigh". Based on the location of the largest population of people with the surname today, Co. Waterford or Co. Tipperary seem to be where the Clan originated. However unusually the earliest known references found to date, dating from 14th and 15th centuries are to be found in Co. Kerry.



The surname means "a descendant of a devotee of Cathach". The surname is of ecclesiastical origin meaning that the family came into existence from within the early Irish monastic tradition. It was common in medieval times for major families to send family members to be educated at monastical communities. Patronage of religious institutions was a means for Clans to gain reputation as well as establish links from which they can later exploit. The monastic community of Inis Cathaigh is the probable origin for the Mulcahy surname. Inis Cathaigh's position within the Shannon estuary seems to support this as the earliest references to bearers of the name seem to have held important position within the nearby religious communities of Inisfallen, Aghadoe and Ardfert.

O'More theory[edit]

There exists a popularly circulated theory regarding the Mulcahy families origins. The theory first proposed by John O'Hart claims that the Mulcahy family descend from the O'More of Laois. O'Hart makes mention of a John O'More who he claims was a younger brother of Rory Caech O'More and who adopted the surname Maolcatha.[1] This theory is almost certainly wrong. O'Hart, intentionally or unintentionally had attributed the origins of the Mulcahy family with O'More on the basis of the name which John O'More had adopted. The name John O'More adopted was not Maolchatha as O'Hart had claimed but actually Maolchathail,[2] and it is from him that the County Laois sept of Ó Maolchathail usually anglicized Mulhall, claim descent. To this day many commercial heraldic outlets continue to pass the traditional arms of the O'More family of Laois, which are "Vert a lion rampant or in chief three mullets of the last", off as those of Mulcahy when there is clearly no connection between the two families.


The Chiefly line for the Mulcahy sept seems to have become extinct relatively early on. Turbulent political events such as the Tudor reconquest and the reformation greatly effected the Irish church and those dependent on it. We have scant references from medieval sources that a County Kerry branch of the family had established something of a political force within the Monastic communities of Kerry. A County Waterford/Tipperary branch had for a long time been thought of as the senior branch of the Family. However this seems to come from unreliable sources such as O'Harts Pedigrees which falsely traces the line back to the O'More's of Laois.

According to the website of the Mulcahy Clan, a new Chiefship claim has been made based on the controversial "ad hoc" Derbfine system. This is an accepted system for restoring hereditary Chiefships for Clans in Scotland long bereft of leadership. According to the website, Mr. Oisín Ó Maolchatha of Dingle, Co. Kerry has been chosen to be the next Chieftain of the Mulcahy Clan .

  • Ballyogaha (Baile Uí gCathaigh), in County Cork, which may or may not have had some connection with the family
  • Mulcahy Middle School, a middle school in the San Joaquin Valley in California
  • Mulcahy Stadium, a baseball stadium in Anchorage, Alaska

+[ Thomas Joseph Mulcahy]] (Born June 1946), Earthquake prevention officer and Cloud counter. Republic of Ireland ( 1966- to present.

Fictional person

See also[edit]


  1. ^ J.O'Hart, Irish Pedigrees, Stem of the Irish Nation
  2. ^ The general armory of England, Scotland, Ireland, and wales, p.715