County Kerry was the ancient home of the Ciarraige, Corco Duibne, Uí Cairpri Luachra and Éoganacht Locha Lein tribes.

The inhabitants of this tract, according to Ptolemy's chart, were in his time designated Velabri or Vellibori; "Hibernice," says Dr. O'Connor, "Siol Ebir, obviously meaning Illiberi Iberiae." They are supposed to have been descended from the Iberi of Spain, to which their country lies opposite; but Camden derives their name from the British Aber, signifying an estuary, thus making it descriptive of the nature of the country. The Lucanij, or "people of the maritime country," were placed by Richard of Cirencester in this county, near Dingle Bay. Ptolemy calls them Luceni, and they appear to be the Lugadii of Irish writers, which in a general sense comprehended all the inhabitants on the southern coast, from the harbor of Waterford to the mouth of the Shannon, though sometimes confined to those of the county of Waterford. The present name of the county is variously derived. Some trace it from Ciar, the eldest son of Fergus, King of Ulster, from whom it was called Carruidhe, or Cair Reeght, that is, "the kingdom of Ciar." According to Ledwich, it was called Cerrigia, or "the rocky country," from Cerrig, or Carric, "a rock." Ciaruidhe, or "the rocky district on the water," from ciar or cer, "a rock," and uidhe, or Uí dha, "a district on the water," was the present barony of Iraghticonnor, on the south bank of the Shannon, and from which may be derived Cerrigia and Kerry. The chiefs of this country were called Hy Cain air Ciaruidhe, by contraction O'Connor Kerry.

This district was sometimes denominated Ciaruidhe Luachra, or "the rocky district on the great lake or water." The great portion of the county lying to the south of the river Mang formed, with the whole county of Cork, the old native sovereignty of Desmond, or South Munster. On the arrival of the English, the O'Connors were in possession of the northern part of Kerry; the middle parts were in possession of the Moriartys: the southern portion was occupied by the O'Sullivans, from whom the district named Dunkerron barony was called O'Sullivan's country; also by the O'Donoghoes, distinguished into the septs of O'Donoghoe More and O'Donoghoe Ross, and by the O'Mahonies.

At the arrival of the Cambro-Normans in the late 12th century, the O'Connor Kerry held the north of the county, the O'Moriartys held the middle parts, the southern portion was occupied by the O'Sullivans, O'Donoghues and O'Mahonies, while the western peninsulas were home to the O'Falvays and O'Sheas of Iveragh and Dingle. Mediveval cantreds of the 13th century included Altry (named for the Altraige) and Akunkerry.

Cenél Cerdraige - referred in the descent from Tigernach mac Ailella Auluimm, the Cerdraige Tuilche Gossa are noted in the Books of Leinster, Lecan and Ballymote. The name is also applied in the Cerdraigi Beirri, from the race of Dairfhine Cerda, at Temair in county Kerry; the Cerdraige Temrach.

The territory of Ciarraige Luachra was said to comprise the northern half of county Kerry including the baronies of Trughenacmy, Clanmorris, and Irachticonnor. Septs of the Ciarraige (Clan na Rory) of County Kerry included Ua Conchobuir Ciarraige (O'Conor Kerry), Ua Muiredaig (O'Murtagh), Ua Neide (O'Neide), among others. Various groups of the Ciarriage, descendants of Ciar, are noted in Western Ireland including those in Connacht.

The Ciarraige Cuirche, or Chuirchi, gave their name to the barony of Kerrycurrihy located south of the city of Cork. Their origins are the same as the Ciarraige Luachra, i.e. descended from an ancient ancestor referred to as Cíar, son of Medb and Fergus. The Uí Torna are noted of Kerricurrihy barony, Co Cork, e.g. Mainistir O dTórna.

Eithlenn, in descent from Fergusa mc Rosa, from whom descend the Orbraige (of Munster) and Bentraige. The territory of Orbraige, in Munster, was located in or near the barony of Orrery (and Kilmore) in northern Co. Cork and possibly into southern co. Limerick. A territory referred to as Benntraige (Bantry) was in west Co. Cork near Bantry Bay, and in Corco Luachra according to Onomasticon Goedelicum. O'Hart (Pedigrees) mentions the sept of O'Beice or Beeky as chief of Beanthraidhe, now the barony of Bantry.