The song is not really Irish, because it doesn't really follow the traditional patterns of Irish folksinging.I did a study on Celtic folksongs for my music classes, Mairi's Wedding was one of them. The tune is from the Lewis Bridal Song, it's named after the Isle of Lewis which makes up one of the major parts of the Hebrides off of Scotland. It's interesting that some people claim it as an Irish song, since it is livelier than most of the more traditional Scottish folksongs. Here is a tidbit of history, most of the Gaels came from Dal Raiti, which is now Ulster, when they settled on the Hebrides, they came under the rule of the Lord of the Isles, Clan Donald. Because of the automony from the Kings of Scotland Gaelic culture flourished and survived for over a thousand years. The Rankin family sang a fine redition from their first album, followed by a traditional Scottish tune that is to follow the singing of Mairi's Wedding. I've been to enough wedding to understand the customs that follows.