Hmm, I'd forgotten that I attempted a translation last year.

Here it is, with the rider that I'm not a Welsh speaker. There will be mistakes.

Blewyn glas ar ddole Teifi
A blade of glass on a bend of Teifi
Tidl a-dl dai
Dwyllodd lawer buwch i foddi
Tricked many a cow into drowning
Tidl a-dl dai
Tidl a-dl do

Llawer merch a ‘nhwyllodd inne
Many a girl tricked me
O’r union ffyrdd i’r anial lwybre
From the straight roads to the remote paths

Beth wy’n hidio gweled bachgen
What do I mind seeing a boy
Yn treto ‘nghariad yn fy nghefen?
Courting my love behind my back?

Ei weld e’n llanw glasied iddi
See him filling a glass for her
Finne’n ddigon siwr ohoni
Me sure enough of her

Petawn ddim ond cael y cyfle
If I only had the chance
Tretawn i ei gariad ynte!
I'd court his love!

Rhoddaf goron wen i’r ‘ffeirad
I'll give a silver crown to the minister
Am roi cwlwm sownd â’m cariad
For giving a sound bond to my love

Coron wedyn i’r un person
Another crown to the same person
Gael fy nwylo bach yn rhyddion!
That kept my little hands free!

‘Rown i’n rhodio rhyw foreuddydd
I was wandering some morning
Rhwng y glaswellt a’r mân goedydd
Between the pasture and the little wood

Cwrddyd wnes â hen gymydog
I met with an old neighbour
Un o’r bradwyr dauwynebog
One of the two-faced brothers

Cynta’ peth ofynnais iddo
The first thing I asked him
“Sut mae caru merch a’i chario?”
“How to love a girl and win her?

“Rho di heibio’i chwmni flwyddyn,”
“Give up her company for her year,”
“Daw i’th garu bob yn ronyn,”
“She will come to love you little by little,”

Fe wnes gyngor ‘r hen ffwl hynny,
I followed the advice of that old fool
Am flwyddyn rhois i heibio’i chwmni
For a year I gave up her company

Es i’n ôl ymhen y flwyddyn
I went back at the end of the year
Gan feddwl cawn ei chwmni wedyn
Thinking afterwards to have her company

Y ferch atebsai, ‘n hawdd ei deall,
The girl would answer, easy to understand,
“Ffaelest ti â chael neb arall?”
“Did you fail to get someone else?”

“Cer di ‘mhell! Na ddeua’n agos!”
“Get far away! Don't come near!”
“Rwy’n priodi cyn pen wythnos!”
“I'm marrying before the end of the week!”

Un ferch arall nid wy’n ‘mofyn,
I'll not ask another girl,
Hi oedd ‘y nghariad er yn blentyn
She was my love since childhood

Es i’r ardd i ddewis powsi
I went to the garden to choose a posy
Heibio’r “Lemons”, heibio’r lili,
Past the “Lemons”, past the lily,

Heibio’r “Pink” a’r “New Carnation”
Past the “Pink” and the “New Carnation”
Powsi ges o ddynad poethon
I had a posy of stinging nettles

Rhosyn gwyrdd yng ngardd y gardner
A green rose in the garden of the gardener
Ac enw hwn yw “Caru’n Ofer”
And the name of this is “Loving Vainly”