If we take the two stanzas and 'translate':

Dread spirits all of black water,
ALL THE SPIRITS OF BLACK (adj) WATER ARE DREAD SPIRITS
Clan Owen's wild banshee
AND THE BAIN SIDHE OF THE OWEN CLAN
Bring no ill wind to him nor us,
(PLEASE (?) DON'T BRING BAD LUCK/FORTUNE TO
My helpless babe and me
MY CHILD AN ME

Chorus

And Holy Mary pitying us
To Heaven for grace doth sue
MARY INTERCEDES ON BEHALF OF THE MOTHER AND CHILD


I'm with Malcolm on that--romanticism. Love the song, though. And the melody is beautiful.