Déisi

Déisi is an Old Irish term that is derived from the word déis, which meant in its original sense a "vassal" or "subject" and, in particular, people who paid rent to a landowner.

In a recent title, Paul MacCotter states "The regional kingdom of Déisi Muman must have existed in roughly its present location from a very early period.

Byrne mentions it was noticed by Eoin MacNeill that a number of the early names in the Eóganachta pedigrees are found in oghams in the Déisi country of Waterford, among them Nia Segamain (NETASEGAMONAS), after the Gaulish war god Segomo.

[3] The epic tells the story of a sept called the Dal Fiachach Suighe, who are expelled from Tara by their kinsman, Cormac mac Airt, and forced to wander homeless.

At some point during this migration from Tara to Munster, one branch of the sept, led by Eochaid Allmuir mac Art Corb, sails across the sea to Britain where, it is said, his descendants later ruled in Demed, the former territory of the Demetae (modern Dyfed).

The historicity of this particular passage of the epic apparently receives partial "confirmation" from a pedigree preserved in the late tenth-century Harleian genealogies, in which the contemporary kings of Dyfed claim descent from Triphun (fl.

450), a great-grandson of Eochaid Allmuir, although the Harleian genealogy itself presents an entirely different version of Triphun's own ancestry in which he descends from a Roman imperial line traced back to St. Helena, whose alleged British origin the genealogist stresses.

[13] This manifest fiction apparently reflects a later attempt to fabricate a more illustrious and/or indigenous lineage for the Dyfed dynasty, especially as other Welsh genealogical material partially confirms the Irish descent of Triphun.

[20] An earlier and frequently cited argument by John V. Kelleher is that this was a political scheme of the Uí Néill, Ireland's most dominant dynasty, whom he argues created the Kingdom of Thomond in the tenth century to further weaken the position of the already divided Eóganachta.

The movement of the Déisi Tuisceart into the modern County Clare is not documented, but it is commonly associated with the "annex" of the region to Munster after the decline of Uí Fiachrach Aidhne power in south Connacht.