The Barddas of Iolo Morganwg, Vol. I., ed. by J. Williams Ab Ithel, , at sacred-texts.com
Some have called God the Father HEN DDIHENYDD, 1 because it is from His nature that all things are derived, and from Him is the beginning of every thing, and in Him is no beginning, for He can not but exist, and nothing can have a beginning without a beginner. And God the Son is called IAU, 2 that is, God under a finite form and corporeity,
p. 220 p. 221
for a finite being cannot otherwise know and perceive God. And when He became man in this world, He was called JESUS CHRIST, for He was not from everlasting under a finite form and body. And the man who believes in Him, and performs the seven works of mercy, shall be delivered from the pain of Abred, and blessed for ever be he who does so. Jesus Christ is also called GOD THE DOVYDD; 1 and He has also other names, such as PERYDD, 2 and GOD THE NER, 3 and GOD THE NAV. 4
219:1 p. 218 That is, " the Ancient and Unoriginated One." The word occurs as one of the designations of the Supreme Being in the Welsh Bible, Dan. vii. 7; in the English Bible it is "the Ancient of days." The following definition of the word is given in one of Iolo Morganwg's Notes;--"Dihenydd--Gwehynwg. Yr Hen Wehynwg, the same as Hen Ddihenydd. (Barddas.) Gwehynwg, sef y tardd i fywydoldeb yn Annwn--the original lifespring, or springing into life at the lowest point of animated existence, or out of the chaotic mass of matter in its utmost state of decomposition."
219:2 p. 219 The word is here taken in the sense of Younger, or as denoting the last manifestation of the Deity.
221:1 "Dovydd;" Domitor; the Tamer.
221:2 "Perydd;" the Causer; the First Cause; the Creator.
221:3 "Ner;" Energy; the Powerful.
221:4 "Nav;" the Former; the Creator. Sion Cent has a Poem on "the Names of God," into which he has introduced all these, with the exception of "Hen Ddihenydd," and "Perydd," thus,--
[paragraph continues] They are also, with many others of undoubtedly Druidic origin, still used by the Cymry as epithets for the Deity.