The first English document using the name "Denbigh" is found 24 October, 1282, under Edward I. [Calendar of Patent Rolls, Vol. 2, p.38-39 ] Before this time, it seems to have been referred to a "Perfedd-wlad" meaning the interior land. There were four "cantrefs" which could be viewed as our counties of today. These were 1) Rhos, 2) Rhyfoniog, 3) Ystard, and 4) Dyffryn. These cantrefs were to play an important role in my own JONES surname family tree.
The first JONES (spelled Johnes) was Robert Johnes, listed as "vicar of Llanvau" [ Llan-fairdyffryn-clwyd] in the records of 1553 - 1555. [bundle 1363/no.55-56] A John Jevans (1538), and a Jeavan ap Griffith ap David ap Tuder (1544) appear before Robert, which show how the spellings were being listed.
Interestingly, it is recorded that "Thomas ap Jevan ap David ap Blethyn, alias Thomas Jones" is clearly listed [bundle 1363/ no. 62] during the same time period 1553 - 1555. This shows the transition from the Welsh naming system to the English surname system.
It is my own JONES family that has its earliest bridge from the Welsh to the English naming system during this transition period, and from this geographic area. What a deal!