Casadh an tSúgáin
I haven’t seen Brooklyn yet,
but I’ve watched all the clips on YouTube and what did I find?
Iarla Ó Lionáird singing Casadh an tSúgáin!!!
He plays a character named Frankie Doran. He flies by in the trailer at 0:37-0:41
I knew my Gaeilge would come in handy.
You can see all the words from the Iarla Ó Lionáird version of the song as recorded by the Gloaming at: https://ancroiait.wordpress.com/2015/09/16/461-casadh-an-tsugain/
I found a book on Munster Irish which helps a bit. Hint: Do=affirmative verbal particle
Here you have a translation of a different-but-definitely-related version of the same song.
And here is that version sung (surprise) by Muhammad Al-Hussaini, from Westminster Institute in London (he also is playing the fiddle). As one commenter said "Nil se go dona."
All I gotta say is dang, but that's some Munstery (or just older) Irish. Which is to be expected since Iarla's from the Muskerry Gaeltacht. Also, if y'all like Iarla, definitely listen to The Gloaming.