This Irish surname, with variant spellings O'Farrell, (O) Ferrall, and cognates O'Farrelly and O'Ferrally, is an Anglicized form of the Old Gaelic Ó Fearghail. The Gaelic prefix "O" indicates "male descendant of", plus the personal byname "Fearghal", composed of the elements "fear", man, and "gal", valour; hence, "descendants" of the man of Valour" (I like that!).
This great sept originated in the Leinster Co. of Longford and their chief known as Lord of Annaly resided at Longphuirt Ui Fearghaill (i.e. O'Farrell's fortress) from which the name of the county derives. So important was the sept that much space is accorded to them in the "Annals of the Four Masters". There were two main branches of the O'Farrell's, the chiefs of which were distinguished as O'Farrell Boy from "buidhe", meaning yellow or Golden, and O'Farrell Bane from ban meaning "fair" or "white". Several of the family distinguished themselves in the Irish brigade in France, and Sir Thomas Farrell (1827 - 1900), was a noted sculptor many of whose statues adorn the city of Dublin.
A Coat of Arms granted to the (O) Farrell family depicts a gold lion rampant on a green shield. The colour symbolizes Hope, Joy and Loyalty in Love. It also reflects the hopes, ambitions and aspirations of its original bearer. On the Crest there is a black greyhound springing from a ducal coronet.
The first recorded spelling of the family name is shown to be that of Father Richard O'Farrell, which was dated circa 1615 - 1663, in Annaly, Co. Longford, during the reign of King James I of England and VI of Scotland (1603 – 1625).
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.