Aongus or Aenghus was the name of the young god of Irish traditions and was a name borne by many legendary heroes. As with most first names, this gave rise to not one but two surnames - MacAenghusa (son of Aenghus) and ╙ hAenghusa/╙ hAenghuis (descendant of Aenghus).
The first was generally anglicised (Mac)Guinness and betimes Maginnis, with the latter anglicised Hennessy, and occasionally Henchy and Hensey.
Both the O and the Mac families became famous in the production of strong drink - Guinness for porter and Hennessy for brandy.
Families of U∅ Aenghusa (descendants of ╙enghus) evolved independently in various parts of Ireland - for example, among the U∅ Failghe and the Dβl Cais - and there were two such families in Co Cork with, apparently, separate origins (Family Names of County Cork: Diarmuid ╙ Murchadha 1985). That of west Cork was called Ihanegus in a document of around 1230, though there are no subsequent mentions in documents.
Some members may have moved into Muskerry, where there is a townland called Ballyhennessy in the parish of Donaghmore. It was written as Ballyenisy in 1558, i.e. Baile U∅ Aonghusa. Ballyhennessy names townlands in counties Clare, Cork, and Kerry.
The other Cork U∅ Aenghusa, about which we will concern ourselves, that of Crichad an Chaoill∅ (in the Fermoy region), occupied Baile idir dβ Abhainn in Tuath U∅ Conaill, to the west of the Fermoy-Mitchelstown road. Ballyderowen. "the town between the two rivers", is now confined to the townland of that name, parish of Kilcrumper, but in earlier times included Uam Cr≤ine (probably Cronohill, parish of Leitrim).
"The U∅ Aenghusa were also connected with St. Molaga`s church of Aghacross, while in the life of Colmβn mac Luachain one of the name was said to be erenagh of Cill ┌ird (Kilworth)".
The Justiciary Rolls (1308-14) lists Maurice, Donald and Padin O Henys in a 1313 hearing at Cork.
The Ormond Deeds notes Odo O Hennessa among the witnesses at Dunmogan to a will in 1519, while a 1575 pardon of John fitz David O Henose of Dunmaghan, gent, is noted in The Irish Fiants of the Tudor Sovereigns (1522-1603).
╙ Murchadha notes: "There is a reference (by James Terry, Athlone Herald, in 1712) to a Maria Hennessy, daughter of John Hennessy, Knight, lord of Dunmahon.". The Fiants list this surname in a variety of spellings - O Hennessy/O Hennesie/O Hennesy etc., among which were Donogh mac Thomas Hennessa alias mac Y Photery, and David og O Henesa, alias Fear Ryata.
In 1564 a grant was made " in the field of Rosponte (New Ross) viz., a great messuage called Britton's great house", then held by Shane O Hennesse and another. A fiant of 1575 lists seven of the name, from places such as Farahy, Oldcastletown, Monanimy, Curraghoo etc., most of which are in the Co Cork barony of Fermoy. The tower-house in Curraghoo (in the parish of Glanworth) may have been a Hennessy stronghold. Curraghoo was the location of John fitz David mac Donough O Henous, Thomas ny Kartyne O Henous, Richard fitz David O Henous and Thomas fitz Richard O Henous, yeomen, pardoned in 1573. In 1621 There was a Thomas O Hennessy at Curraghoo.
A Census of Ireland (1659) lists (O)Hennessys among the principal Irish names in the Co Clare baronies of Inchiquin and Tulla; in the Co. Tipperary barony of Slievardagh; in Kilkenny city and its county, and in the barony of Fassaghdinan, and in Waterford city and its county. Hennessys were tituladoes in Ballyasheea, Agheram and in Drumcurren west, all in Co Clare.
Taylor & Skinner's 1778 Maps of the Roads of Ireland shows Hennessy Esq., at Ballymacmoy, Co Cork. Here was born Richard Hennessy, in 1720. He emigrated to join his Wild Geese relatives in France, becoming an officer in Dillon's regiment, and fighting at Fontenoy.
His son Richard was the founder of the well-known Hennessy brandy family of Cognac. His other son married a Martell, another well-known brandy family.
The 1814 Directory has Hennessy residences at Fort William, Doneraile, Co Cork, and Laherdane, Listowel, Co Kerry.
Owners of Land of One Acre and Upwards (1876) lists Hennessy holdings in counties Kildare, Cork, Kerry, Tipperary, and Galway. The greatest number were in Co Cork, the largest - of 1,431 acres - at Ballindeasig, Ballyfoyle.
Current telephone directories list 1,184 Hennessy entries, with almost 800 of these in south Leinster, and Munster. There are some two dozen in The Phone Book of Northern Ireland, with four ╙ hAonghusa entries - one each in counties Dublin, Kildare, Tipperary, and Galway.