[2] In some cases, it may also have independently arisen by a similar anglicization of a likely-distinct Irish patronymic, Ó Maol Phádraig,[3] "Descendent of the Follower of (St.) Patrick", or in rare cases as a genuine Anglo-Irish patronymic[1] incorporating the Norman French fiz ('son of') and the male name Patrick.
[citation needed] Giolla Phádraig (meaning "the devotee of [Saint] Patrick", also one of origins of the surname Kilpatrick) was the personal name of Gilla Patráic mac Donnchada, a tenth-century king of Ossory.
His sons were subsequently styled Mac Giolla Phádraig (meaning, son of Giolla Phádraig), and gave rise to a dynasty of Kings of Ossory that bore this patronymic as a dynastic name.
In the 16th century, as part of the process of king Henry VIII's surrender and regrant scheme to anglicize the Irish nobility, some members of the clan were legally obligated to render their surname as Fitz-Patrick or Fitzpatrick as part of the agreed terms with the Crown.
[citation needed] The Fitzpatrick surname may have also been adopted later amongst other unrelated Irish families, such as the Maguires of Fermanagh.