adapted from the original by Joseph Campbell aka Seosamh MacCathmhaoil
Where lagan streams sing lullabies
There blows a lily fair.
The twilight gleam is in her eye
The night is on her hair.
And like a love sick leannan si
She hath my heart in thrall;
No life have I, no liberty
For love is lord of all.
And often when the beetle's horn
Has lulled the eve to sleep
I steal into her shieling lorn
And through the doorway creep.
There on the cricket's singing stone
She makes the bogwood fire
And sings in sweet and undertone
The song of heart's desire.
"Lagan" means something one throws away in hopes that it will return. From what I remember it seems people would offer gifts to gods or supernatural beings and toss them in the "lagan stream", hoping these items would come back.
"Leannan si" is a beautiful, but deadly spirit who appeared (conviently) in the guise of a woman. She lured young men to their doom, bascially. Similar to a siren in Greek mythology.
I have no freakin' clue what a "beetle's horn" is, except in the song is sounds kinda phallic. Hence, the sword references. And then sex. And death. Of course.
"Shieling lorn" is just a little hut. Like Princess Isabella's Sooper Sekret Hideway and Sexin' Spot (tm) in the film.
Also: the thistle, especially as used in the film, is a symbol of Scotland. Just FYI.