Duhallow is a barony in northwest Cork. The area that includes Duhallow was once called Ir-luachair and included a part of County Kerry. Researchers familiar with the O'Kief Cosh Mang collection of historical materials will recognize the area. Dermot MacCarthy built Drishane Castle.

From JCHAS:

Duhallow. Duthaig-Ealla, the country of the Allo, a river flowing through the north-west part of the barony. The district including this barony was, in ancient times, called Ir-luachair, and extended into Kerry. In the Book of Rights, which records the privileges of the Irish kings, the following refers to Duhallow: -

"Seven steeds [are due] to the King of Killarney,
Seven drinking-horns, seven swords [imported] from afar, Seven shields at the smallest reckoning, Seven beautiful hounds in Irluachair."

The MacDonoghs, styled princes of Duhallow, a branch of the great sept of MacCarthys, were chiefs of this district till 1641. In 1436 Dermod MacCarthy built Drishane castle. Later we read of Donogh Oge MacCarthy (Young MacCarthy), lord of Ealla, in these good old times, killing "Barry More John, the choicest of the English youths in Ireland," on a Christmas day. In Elizabeth's reign MacDonogh MacCarthy commenced the erection of a castle at Kanturk, which was stopped by order of Council. Their feudatories were O'Keeffe, chief of Pobble O'Keeffe (a portion of which territory was an undisposed forfeiture until a very recent period); MacAuliff, chief of Clan Auliff; and O'Callaghan (now represented by Viscounts Lismore), chief of the territory called Pobble O'Callaghan, west of Mallow. The O'Keeffes were formerly an important southern sept; until dispossessed at the Norman invasion, their principality extended over the present baronies of Fermoy, Orrery and Kilmore, and Condons. The subsequent fallen fortunes of the O'Keeffes is satirized in the Tribes of Ireland (by the famous Irish poet Aenghus O'Daly, sixteenth century, for which he paid the penalty of his life, translated and annotated by Dr. O'Donovan), a venomous lampoon on the poverty, meanness, and want of hospitality of the Irish chieftains. The following is a translation, or paraphrase, of that part referring to the O'Keeffes-

"The ragged O'Keeffe, he shivers and shakes,
The sad ragamuffin, he hasn't the stuff in
His carcase to battle with agues and aches,
But I spare him the luckless;
Poor devil - the cloakless are always the pluckless."

Of the MacDonoghs he writes: -

"At Easter I was in the house of MacDonogh;
He was my friend! My girdle he tightened;
His people and feast were such
As if Easter were Good Friday."

This data might be lost for Duhallow. Searching for a substitute.