The top 100 Irish last names explained

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Fitzpatrick - Mac Giolla Phádraig (devotee of St. Patrick). The only Fitz name of Gaelic-Irish origin, the main sept being located in Ossory. The name is numerous also in Fermanagh where families so called are said to be of MacGuire stock.

Flanagan - Ó Flannagáin (flann, ruddy or red). Of the several septs of the name that of Connacht is the most important: their chief ranked as one of the ‘royal lords’ under O’Connor, King of Connacht.

Flood - Some Floods are of English extraction, but in Ireland they are plainly Ó Maoltuile or Mac Maoltuile, abbreviated to Mac an Tuile and Mac Tuile anglicized MacAtilla or MacTully as well as Flood. Tuile means flood but probably it is here for toile, gen. of toil, will, i.e. the will of God. In parts of Ulster Flood is used for the Welsh Floyd. (Welsh llwyd. Grey)

(O) Flynn - Flyng  ÓFloinn (flann, ruddy). This numerous and widespread name originated in a number of different places, including Kerry and Clare. Of the two in Co. Cork one was a branch of the Corca Laoidhe, the other, lords of Muskerylinn (Muiscre Uí Fhloinn); in north Connacht the O’Flynns were leading men under the royal O’Connors, and there was also an erenagh family there; while further West on the shores of Lough Conn another distinct erenagh family was located. For the name in Ulster is an indigenous sept.

(O) Gallagher - ÓGallchobhair. This name (gallchobhar, foreign help) has at least 23 variant spellings in anglicized forms, several of them beginning with Gol instead of Gal. It is that of one of the principal septs of Donegal.

MacGowan -  Mac an Ghabhann, Mac Gabhann. In Co. Cavan, the homeland of this sept, the name has been widely changed by translation to Smith (though Smithson was a truer translation); but in outlying areas of Breffny MacGowan is retained.

(O) Grady -  Ó Grádaigh (gráda, illustrious). A Dalcassian sept. The leading family went to Co. Limerick but the majority are still Clare where the prefix O is retained more than anywhere else. An important branch changed their name to Brady in the late sixteenth century. The well-known name Grady has to a large extent absorbed the rarer Gready which is properly a Mayo name.  This resulted in the name of Grady being numerous in north Connacht and adjacent areas of Ulster.

MacGrath - Magrath  Mac Graith, Mag Raith. The personal name in this case is Craith not Raith. The name of two distinct septs; viz. (i) that of Thomond who supplied hereditary ollamhs in poetry to the O’Briens, a branch of whom migrated to Co. Wexford; and (ii) of Termon MacGrath in north-west Ulster, a co-arb family. MacGrath is often called MacGraw in Co. Down and MacGragh in Donegal.

(O) Hagan - Ó hÁgáin. It is fairly well established that this name was originally Ó hÓgáin (from óg, young). It is that of an important Ulster sept: the leading family was of Tullahogue. Ó hAodhagáin, also anglicized O’Hagan, is said to be a distinct sep of Oriel, but owing to proximity of Co. Tyrone and Armagh, they are now indistinguishable. The Offaly name mentioned by Woulfe is now extinct or absorbed by Egan in Leinster. ÉO Dowd (a) Ó Dubhda. A branch settled in Kerry where they are called Doody. Another small sept of Ó Dubhda Co. Derry and they are usually Duddy now.

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