See his autobiographies, George (1961) and Emlyn (1973).
The name derives from am (around, on both sides of) and glyn (valley), the valley in question being presumably the Cuch. Its area was about 217 km2. It was divided by the River Cuch into the commotes of Emlyn Is Cuch (to the west) and Emlyn Uwch Cuch to the east. Its civil headquarters were divided between Cilgerran in the lower commote and Newcastle Emlyn in the upper. Its ecclesiastical centre (and perhaps, in the Age of the Saints, the seat of a bishop) was the church of St Llawddog at Cenarth.
The cantref was made part of the Norman March in the 12th century, and many castles were built, including those of Cilgerran and Newcastle Emlyn. Nevertheless, the area remained Welsh speaking, as it continues today.
At the time of the Acts of Union, the cantref was split between the newly-formed counties, when Emlyn Is Cuch became Cilgerran hundred, Pembrokeshire and Emlyn Uwch Cuch was merged into Elfed hundred, Carmarthenshire. Its name lives on in several local placenames, including Newcastle Emlyn.