One translation (of two verses) is:

Myfanwy
English words John S Cottam

Why art thou silent, Oh Myfanwy?
What dims thine eye & clouds thy brow?
Those cheeks which once with love blushed on me,
Why are they pale and bloodless now?
Why bite those lips that loved my kisses?
Where is the smile that won my heart?
Why silent be?
Oh speak to me,
Speak, love, once more before we part.

What have I done to thee, Myfanwy,
To change thy love to scorn for me?
Am I too fond, or thou too fickle?
Or art thou being false to me?
Thou art my only love forever,
Wilt thou thy promise true fulfil?
Thou made us part,
And broke my heart.
So now, Myfanwy, now Farewell.