It often happens in comparing ancient stories with modern topography, that the old names are retained while
the boundaries of the territory which they indicated are changed. Not infrequently, the names of petty Celtic kingdoms were
applied to modern counties. This is the case with Dyved, the country inhabited by the Dimetae of the Romans. It is now generally
considered to apply only to the county of Pembroke. It once included also the counties of Carmarthen and Cardigan, forming, in
fact, the western, while Gwent formed the eastern division of South Wales.
There appears, however, to have been an exception to this general division, a portion of Cardigan having been
once exclusively termed Ceredigiawn, and one-third part of Carmarthenshire having been included in the District of Rheged,
called subsequently "Cantrev Bychan and Kidwelly."
Lewis Dwnn, in the reign of Elizabeth, thus describes the ancient boundaries of Dyved, as he understood them
to have been: -
"The kingdom of Dyved formerly extended between the rivers Teivy and Towy, from
Llyn Teivy and the source of the Towy to St. David's, and the centre of this kingdom was the Dark-Gate, in Carmarthen,
and there is at this day a record of these boundaries in an old parchment book of the Bishop of St. David's."
According to this, Dyved would appear to have consisted of about a sixth part of Cardiganshire, two-thirds
of the county of Carmarthen, and the whole county of Pembroke.
It is evident, however, that at the time the Mabinogi of Pwyll was committed to writing, Dyved was restricted
to the Cantrevs (or Hundreds) of Arberth (or Narberth): Dan Gleddyv, y Coed, Penvro, Rhos, Pebidiog, and Cenmaes, to which
we are told that Pryderi added the three Cantrevs of Ystrad Tywi, or Carmarthenshire, Cantrev Bychan, Cantrev Mawr, and
Cantrev Eginawg, together with the four Cantrevs of Ceredigiawn, Cantrev Emlyn, Cantrev Caer Wedws, Cantrev Mabwyniawn,
and Cantrev Gwarthav, which seven Cantrevs were classed together under the appellation of Seissyllwch. The addition made
by Pryderi probably restored Dyved to its original extent at the time of the Romans.