This is the English version by James Clarence Mangan. As Martin Ryan remarked in an earlier message on this thread, this version is a short one at only three verses. There is formal rhythm and rhyme in Mangan's version. Thus it is likely not to be all that accurate a translation from the Gaelic. I cannot answer the inevitable question, whether or not Mangan's English is intended to fit any tune, if it is singable to a melody associated with the original. After data-entry of Mangan's English versions, I will conclude this post with bibliography source; it is from the Collected Works of James Clarence Mangan, which has only been around since the 1990's.

T H E    C O O L U N    An Cul Fionn: "The maiden of the fair flowing locks"

Have you e'er seen the Coolun when daylight's declining,
With sweet fairy features, and shoes brightly shining?
Though many's the youth her blue eyes have left pining,
She slights them, for all their soft sighing and whining.

Have you e'er on a summer's day, wandering over
The hills, O, young man, met my beautiful rover?
Sun-bright is the neck that her golden locks cover --
Yet each paltry creature thinks she is his lover!

Have you e'er seen my Fair, on the strand, in her bower,
With gold-ringed hands, culling flower after flower?
O! nobly he said it, brave Admiral Power,
That her hand was worth more than all Erin for dower.

pp. 169 - 170, Volume 4, The Collected Works of James Clarence Mangan: Poems
(Volume 4 covers 1848 - 1912 publications, mostly posthumous)
Author: James Clarence Mangan
Editors: Jacques Chuto, Tadhg O Dushlaine, Peter Van de Kamp
Publisher: Dublin, and Portland OR: Irish Academic Press, 1999

Endnote: "Admiral Power": this character has not been identified.