Translated from the Welsh means ……SeaMonster.
I think it refers to the legend of the leviathan that lives off the West Wales coast in Cardigan Bay.
This is the way it’s played in Llandeilo , but I have seen it notated in D major somewhere, I’ll put the ABC’s for it ‘now, in a minute’. Hope Dmix is the right mode, or is it just plain old E min?
Say;—— Moor Gower.
Just discovered this tune was written by Simon Owen and has been recorded a couple of times. By Glenorfa and Calan.
The B in the ‘C’ part is played as an A though.
Glenorfa is I think Y Glerorfa. (Y Glerorfa yn Fyw)
It’s also on "O Groth y Ddaear" by Gwilym Rhys Bowen.
Parts A and B are Mix, but C is Dorian and the F is natural not sharp.
The late Simon Owen was a piper of S. Welsh origin who lived and worked in Oxford. He died sadly young. I only met him once when we were both tutors at a Welsh tunes workshop. I actually had the tune from his friend, the late Jeff Hughes, who notated it from Simon’s playing. The title is actually Cornish (no circumflex on the o) and refers to a Cornish legend. It does indeed mean "sea giant" in both languages.
This downloadable document of mine has some further background on this tune and a correct notation.