The Fitzpatrick surname is the most common variant derived from the Gaelic clan Mac Giolla Phádraig, which is frequently Anglicized to Mac Gilla Patric, MacGillapatrick, McGilPatrick, Macllpatrick, Mcllpatrick or Kilpatrick. In addition to these readily recognizable variations, one of the clan members changed his surname to the Gaelic equivalent of Geoffrey and this sept of the family has numerous variations including MacSherra, McSherra, McShera, McSheera, Shera, Sherar, Sherra and Sheera. The name Fitzpatrick does not appear until the late 1500s when Sir Barnaby Fitzpatrick, Second Baron of Upper Ossory, who is raised in the English court, combines the Norman Fitz with the Gaelic Patrick. Variations of this name include Fitz-Patrick and Fitzpatrick.
There are family researchers who claim to have established a pedigree of this clan showing descent from King Milesius (also spelled Mil Espaine in some references) who was a Gaelic king of a portion of what is now Spain. He was married to an Egyptian princess whose name was Scota who he apparently married as part of an alliance against the King of Ethiopia. In the 5th century, he sent either a trading mission or an army headed by one of his sons who was killed by the resident Irish kings (the Danans). The enraged King Milesius prepared a fleet and sent an army to take revenge but died before being able to fulfill his quest. His wife Scota, uncle Ith and his sons completed the mission and conquered at least part of Ireland.
Heremon, the eldest son of King Milesius and his brothers Heber, Ir and Ilthe ruled the newly conquered territory. According to one source, they initially named the land Scotia in honor of their mother who by at least one account was killed in battle. Some historical references record that Scotia Major was initially used as a name for Ireland and Scotia Minor was used as a name for Scotland which had also been conquered. There are at least three versions of how the name became Ireland but according to one source, that is was named after Ir (youngest son of King Milesius) and was initially known as Ir-land.
The earliest that a name recognizable as being of our family first appears in the 9th century with the issue of Doncadh (also known as Doncadh macCellaig), who is a descendent of King Melesius. Doncadh was the King of Ossory (Osraige in Gaelic). His son was named Gilla Patraic I and the clan Mac Giolla Phadraig would arise from his descendants. Ossory lies within the Kingdon of Leinster (see map). While its size and dimensions of Ossory have varied over the centuries, in the 12th century it comprised most of the modern county of Kilkenny and the western portion of the modern County Laois (also known as Queens County at one point in history). While the clan Mac Giolla Phadraig were the historical rulers of this region there were many other important smaller Gaelic families (septs) including O’Phelan (Whelan), O’Brody, O’Brophy, O’Coveney, Dunphy, O’Gloherny (Glory), MacBreen, O’Broder (Broderick), O’Delany, O’Horahan, O’Kealy, O’Brennan and O’Carroll. It is likely that the Mac Giolla Phadraig family both intermarried and at times fought for control of Ossory with these less powerful families. The clan Mac Giolla Phadraig would eventually loose control over everything except the northern part which is known as Upper Ossory.