As a follow up to DG's post, I think Irish singers have a tendency to come to "own" the songs as performers emotionally, and that comes through in their performances of material, regardless of the song's source. Of course, the same can be said of other cultural groups too, but the "emotional truth" of the song is central to Irish traditional singers interpretation of any song they perform. The words often tend to matter less than the emotion evoked by the song. It is the emotion that is being communicated in a good performance.

Once an individual "owns" a song in this way, in the Irish tradition, it often does become "their" song, and other singers likely won't perform it publicly. It is a very different idea of ownership of song than the standard used by folk song collectors interested in attributing a song to a specific nation/ancestral group. Which is another issue I don't see being discussed here much, though I don't know if gnu was half serious or half joking when he said 'perhaps the Irish perform the songs better'.

Misattribution of the national origin of the composers of songs (folk or pop or jazz or gospel) is very common. So why is it that the British/Scottish/English focus so much on the misattribution of songs to the Irish, and not the other way around, or about other cultural groups/nationalities, d'you suppose? Prejudice is the only rational answer I can come with. I'm not suggesting it to be inflammatory at all. Declan asked, and I gave an answer I believe is at least partially correct.