Fahy in Irish is O Fathaigh, probably from fothadh meaning "base" or "foundation". Another, rarer, English version of the name is "Vahey". Strangely, it has also been anglicised as "Green" because of a mistaken association with faithce, meaning "a lawn" or "green". The name still has a very strong association with Co. Galway, where the historic homeland was situated. The area of the family's power was around the modern town of Loughrea in the south of the county, and they retained their property in the region until the catastrophe of the seventeenth century. The surname is still most plentiful in this area, despite the upheavals and migrations which have spread the name quite widely throughout Ireland. The best-known bearer of the name was Francis Arthur Fahy (1854-1935), songwriter and literary man, who paved the way for the Irish Literary Revival through his lifelong involvement with the Gaelic League and the London Irish Literary Society.
"Fahy" appears as an element in many Irish placenames, meaning a green or level grassy place, and this may have something to do with the occasional anglicisation of O Fathaigh as Green. Fahysvillage in Athenry parish certainly records the family name, however.
In 1890 there were 114 births of the name, with more than half of these in Co. Galway, and particular concentrations also in the adjoining counties of Mayo and Tipperary. As well as Fahy, Green has been used as an anglicisation of a number of other Irish originals, including O Grianain, Mac Glasain and Mac Giolla Ghlais, either through a phonetic resemblance or a supposed connection with glas, meaning the colour green. For this reason, and of course because many English settlers bore the name, it is now very widespread throughout the country.
Father Anthony Fahy (1805-1871) became famous in his adopted country, Argentina. The fahy Institute there is named for him.
.Francis Fahy (1880-1945) played a prominent role in the War of Independence and became ceann comhairle (speaker) of the Irish parliament Dail Eireann after independence.
David Greene (1915-1981) was a senior professor in the School of Celtic Studies in the Dublin Institute for Advanced Studies from 1967 to 1981 and was well known in Irish life for the rigour and vigour of Hs views.
Green(e) is an extremely common English surname, generally referring to someone who lived near a village green. Many Irish bearers of the name, particularly in Ulster, are probably of this connection. However, Green(e) was also used as the anglicised version of a wide variety of Irish names containing uaithne, 'green', or glas, "grey-green". O hUaithnigh, anglicised as both "Green" and the phonetic "Hooney", arose in Co. Cork. In Co. Clare the original, from the same Irish stem, was O hUaithnigh, more rarely anglicised as "Hooneen"and "Huneen". In Ulster, Mac Glasin, "McGlashan", and Mac Giolla Ghlais, "McAlesher", relatively common in counties Antrim and Derry, also became Green. Further, O Griana, Mac Griana, found in north-west Ulster, and O Grianain, from counties Cavan and Sligo, were also phonetically rendered as Green, although the root of the names is the Irish grian, meaning "sun".