The same book also quotes the North Wales version. Which, for the sake of completion...

UNWAITH ETO ("HOB Y DERI DAN-NO")
Traditional (Eng. words Walter Maynard)

Unwaith eto mi ddywedaf
"Hob y deri danno,"
Sian, fwyn, Sian?
Nid oes tês ar amser gauaf-
Dyna ganu eto,
Sian, fwyn, Sian.
Ond mae Sion yn wrth heneiddio-
Dal di sylw Sian.
Efo cariad yn gwefreiddio;
Sian fwyn tyrd i'r llwyn,
Seinaf enw Siani fwyn, Sian, fwyn Sian.

Llawer gauaf haf a gwanwyn
"Hob y deri danno,"
Sian, fwyn, Sian!
Wnaeth fi'n foel a thithau'n felyn:-
Dyna ganu eto,
Sian, fwyn, Sian.
Nid yw henaint o un d'ioni:-
Dal di sylw Sian.
I wneud cariad ieuanc ocri:
Sian fwyn tyrd i'r llwyn,
Seinaf enw Siani fwyn, Sian, fwyn Sian.


All the day I sigh and say, love
"Hob y deri danno," Jane, sweet Jane:
All the night I dream or pray, love,
"Hob y deri danno". Jane, sweet Jane.
Ah! since that first time we met,
I do naught but complain,
Tho' I fear thou dost forget,
I hope on still in vain.
All night and day,I sigh for thee, Jane sweet Jane.

And as oft I sigh and say, love
"Hob y deri danno," Jane, sweet Jane!
I ask why thou dost delay, love
"Hob y deri danno". Jane, sweet Jane.
Can it be thou heedest not if we ne'er meet again?
Am I then so soon forgot, and do I love in vain,
All night and day I sigh for thee, Jane, sweet Jane.


Source: "The Songs of Wales" Edited Brinley Richards; pub. Boosey & Co. (fourth edition 1879) P 66

Nigel