It is now used as a shorthand for the various realms united under the House of Dinefwr, but that Deheubarth itself was not considered a proper kingdom on the model of Gwynedd, Powys, or Dyfed[5] is shown by its rendering in Latin as dextralis pars or as Britonnes dexterales ("the Southern Britons") and not as a named land.

[6] In the oldest British writers, Deheubarth was used for all of modern Wales to distinguish it from Hen Ogledd (Y Gogledd), the northern lands whence Cunedda originated.

Caerleon was previously the principal court of the area, but Hywel's dynasty fortified and built up a new base at Dinefwr, near Llandeilo, giving them their name.

The long and capable rule of Gruffydd's son the Lord Rhys – and the civil wars that followed Owain's death in Gwynedd – briefly permitted the South to reassert the hegemony Hywel Dda had enjoyed two centuries before.

Following the conquest of Wales by Edward I, the South was divided into the historic counties of Cardiganshire, Carmarthenshire and Pembrokeshire by the Statute of Rhuddlan.

One son, Rhygyfarch (Latin: Ricemarchus) of Llanbadarn Fawr, wrote the Life of Saint David and another, Ieuan, was a skilful scribe and illuminator.