In modern Irish the word for province is cúige (pl. cúigeadh). The modern Irish term derives from the Old Irish cóiced (pl. cóiceda) which literally meant "a fifth". This term appears in 8th century law texts such as Miadslechta and in the legendary tales of the Ulster Cycle where it refers to the five kingdoms of the "Pentarchy". In the 12th-century Lebor na Cert (Book of Rights), the term means province, seemingly having lost its fractional meaning with seven cúigeadh listed. Similarly this seems to be the case in regards to titles with the Annals of Ulster using the term rex in Chóicid (king of the fifth/province) for certain overkings.
The origins of the provinces of Ireland can be traced to the medieval cóiceda (literally "fifths") or "over-kingdoms" of Ireland. There were theoretically five such over-kingdoms, however in reality during the historical period there were always more. At the start of the 9th-century the following are listed: Airgíalla, Connachta, Laigin, Northern Uí Néill (Ailech), Southern Uí Néill (Mide), Mumu, and Ulaid. These seven over-kingdoms are again listed in the 12th-century Lebor na Cert.
Each over-kingdom was divided into smaller territorial units, the definition of which, whilst not consistent in Irish law tracts, followed a pattern of different grades. In theory in the early medieval period:
Paul MacCotter proposes the following structure of lordship in the 12th-century: High-king of Ireland; semi-provincial king, such as Connacht, Ulaid, Desmumu; regional king, such as Dál Fiatach and Uí Fhiachrach Aidni; local king or king of a trícha cét, such as Leth Cathail or Cenél Guaire; and taísig túaithe at the bottom.