The Fagan Name and its Variants
According to the Internet Surname Database:
This interesting surname is of Irish origin, but the source is uncertain. The Gaelic form is "O'Faodhagáin", but a personal name Faodghagan is not known, and it may be a Gaelicized version of a surname of Norman origin. A number of Irish bearers of this name are descended from Patrick Fagan, who owned estates in County Meath in the 13th Century. According to tradition, his name was originally O' Hagan and he assumed the name Fagan at the command of King John, for reasons which are unclear. For many Centuries the surname has been associated with Counties Dublin and Meath; a branch of the family was also found in Kerry and another in Cork city, where Christopher Fagan took refuge in 1497. He had been a supporter of Perkin Warbeck's claim to the throne, and Cork was solidly behind that pretender. Among the recordings in Ireland are the christenings of James Fagan on December 17th 1670 at St. Peter and St. Kevin, Dublin and of John, son of John and Sarah Fagan on December 16th 1684 at St. Michan, Dublin. The first recorded spelling of the family name is shown to be that of William Fagan, which was dated 1200, Dublin City, Ireland, during the reign of King John, known as "Lackland", 1199 - 1216. Surnames became necessary when governments introduced personal taxation. In England this was known as Poll Tax. Throughout the centuries, surnames in every country have continued to "develop" often leading to astonishing variants of the original spelling.
According to GoIreland.com:
In spite of its very Irish appearance (gan is one of the most common terminations of Irish surnames) Fagan must be regarded (subject to a reservation to be mentioned later) as a family name of Norman origin. At the same time it must be pointed out that it is not an English name. It is derived from the Latin word paganus. For many centuries it has been associated with Counties Dublin and Meath. As early as the year 1200 one William Fagan was the owner of extensive house property in the city of Dublin and fifty years later we find the family firmly established in the neighbouring counties with a seat, acquired a little later, at Feltrim, Co. Dublin. A branch of this family was also found in Kerry and another in Cork city where Christopher Fagan took refuge in 1497 - he had been a supporter of Perkin Warbeck's claim to the throne and Cork was solidly behind that pretender. From the Kerry branch were descended the Fagans who distinguished themselves in the service of France in the eighteenth century and were ennobled in that country. The name is not really numerous in Ireland - it is estimated that about two thousand of the population are so called : almost all these are natives of Leinster, fifty per cent of whom are Dubliners. There is also, it is true, a Gaelic Irish family of O Faodhagain, anglicized Fagan, which belongs to Co. Louth: it may be a corrupt form of the well known name O'Hagan but Fr. John Ryan thinks not. One of these, Edmund O'Fagan, was an officer in the Ultonia regiment of the Spanish army in 1778. While the fact that Fagan is in most cases of Norman origin is accepted. Fr. John Ryan disagrees with the statement, made by Fr. Woulfe and here that O Faoghagain is a variant of O hAodhagan (O'Hagan) and other scholars concur. They say it is a distinct sept of eastern Airghialla (Oriel). There Fagan, Fegan, Feighan and Feehan are numerous and much confused; probably these all derive from O'Faodhagain. The two best known Fagans in the past were Robert Fagan (1745-1816), born in Cork, who was a diplomat and portrait painter; and James Fleming Fagan (1828-1893), American planter, soldier and public official of Irish descent.
According to Ancestry.com:
Fagan Name Meaning
Gaelicized version of a surname of Norman origin, from the personal name Pagan meaning 'rustic'. In some cases it is a reduced Anglicized form of Gaelic Ó Fágáin or Ó Faodhagáin, which are probably dialect forms of Ó hÓgáin (see Hogan, Hagan) and Ó hAodhagáin (see Hagan). Irish lenited f (spelled fh) is soundless, and a number of words beginning with vowels have gained an initial f in some dialects; such seems to be the case here. occasionally an Anglicized form of Mac Phaidín (see McFadden) or Ó Fiacháin (see Feehan).
According to Patronymica Britannica, a dictionary of the family names of the United Kingdom By Mark Antony Lower, Published 1860:
FAGAN. A corruption of the patronymical O'Hagan. The Fagans of Feltrim, co. Cork, deduce themselves from Patrick O'Hagan, who opposed the invasion of Ireland by the Anglo-Normans in the XII cent. See B.L.G.[Burke's Landed Gentry]
O'FAGAN. See Pagan. Mr. D'Alton's account is, however, different from that there given. He says, that "the family are by some considered of English descent" The name seems to have been well established in Meath in the XII century.