The great king Maelgwyn was reigning among the British, in Gwynedd, for his ancestors, Cunedda, with his sons, to the number of eight2, had come from the north, from the country of Manaw Gododdin, one hundred and forty-six years years before Maelgwyn reigned, and expelled the Irish from these countries, with immense slaughter, so that they never again returned to inhabit them.
From the Historia Brittonum Chapter 62 1
This is the foundation legend of Gwynedd; of how Cunedda, a prince from the district of Manaw in the North British kingdom of Gododdin came south to drive out the Irish raiders from north Wales, and hence establish a kingdom.
The Historia Brittonum does not name the sons, for that information we have to turn to the Welsh Genealogies contained in the Harleian MS 3859, which names not only the eight sons that came, but the ninth that did not;
Hec sunt nomina filiorum Cuneda quorum numerus erat ix: Typipaun primogenitus qui mortuus in regione que uocatur Manau Guodotin et non uenit huc cum patre suo et cum fratribus suis predictis. Meriaun filius eius diuisit possessiones inter fratres suos: ii Osmail, iii Rumaun, iiii Dunaut, v Ceretic, vi Abloyc, vii Enniaun girt, viii Docmail, ix Etern
which I believe would be translated as;
These are the names of the sons of Cunedda who numbered nine: Typaun the firstborn who died in the land named Manaw Gododdin and so did not go with his fathers and his aforesaid brothers. Meirion his son divided his possessions between his brothers: 2 Osmail, 3 Rhufon, 4 Dunod, 5 Ceredig, 6 Aflog, 7 Einion Yrth, 8 Dogfael, 9 Edyrn.
The story is that each of these sons received a portion of territory as his inheritance, which was then named after them. The districts which preserved their names were therefore as follows;
Conveniently for the rulers of Gwynedd all these territories were strategically situated around the borders of the core of Gwynedd and just the sort of places that an expansionist minded king of Gwynedd would covet as his own. 3 Such is often the nature of medieval genealogies and histories; conceived by an imaginative and compliant cleric to serve the politics of the day. In this case the politics of tenth and eleventh century Wales, when the heirs of Rhodri Fawr sought to emulate their ancestor and widen their dominion.
Einion Yrth it will be noted, is the single son that does not lend his name to anything, simply because it was Einion Yrth who inherited Gwynedd itself. There is no explanation provided as to why the kingdom itself would not have passed to either Meirion, as the heir to the eldest son Typaun, or to Osmail, as the oldest surviving son. One can only presume that there was some mystical significance in having Einion Yrth, Maelgwyn's alleged grandfather as the seventh son of Cunedda.
NOTES
1 The Latin text from the Theodore Mommsen edition goes;
Mailcunus magnus rex apud Brittones regnabat, id est in regione Guenedotae, quia atavus illius, id est Cunedag, cum filiis suis, quorum numerus octo erat, venerat prius de parte sinistrali, id est de regione quae vocatur Manau Guotodin, centum quadraginta sex annis antequam Mailcun regnaret, et Scottos cum ingentissima clade expulerunt ab istis regionibus et nusquam reversi sunt iterum ad habitandum.
The phrase venerat prius de parte sinistrali literally means "had come before from the left-hand part" but usually seems to get translated as "from the north"; which presumably means that Britain was conceived as lying sideways with east pointing 'up'.
2 Although so corrupt and varied are some of the texts of the Historia Brittonum, that some versions refer to as many as twelve sons.
3 One could make an exception for Osmaeliog, or Holyhead Island, which is a comparatively insignificantchunk of rock lying off the coast of Anglesey, which harfly equates in terms of an inheritance with the whole of Ceredigion.