I'm Brazilian too and it's nice to see another one interested in Gàidhlig!
Well, about the translation to:
"Coisich, a rùin (hù il oro),
cum do ghalladh rium (o hi ibh o);
beir soraidh bhuam (hù il oro),
dha na Hearadh (boch orainn o)."
The thing is, in Scottish Gaelic music there are many vocals with no meaning really, I guess especially the waulking songs, like Còisich, a Rùin. That's why you don't find translation to " hù il oro, o hi ibh o", etc, etc