And Rose of Aranmore is a different song; but Allendale is the name of Parnell's gaff, and is definitely taken here (in Ireland) as being about K O'Shea.

As for Danny Boy, the tune was collected by Lady Londonderry, who was (as it happens) an Irishwoman who wandered the hills of her estates and beyond collecting traditional Irish music at a time when it was in danger of being lost, and so it is called the Londonderry Air; I don't know exactly where the maudlin words come from, but as far as I know they are, unfortunately, of Irish origin.

As for the Irish stealing tunes, I'm actually not aware of any that have been stolen - though I'm certainly aware of tunes held in common between, for instance, Ireland and Poland.

Anyway, since this thread is a blatant attempt (quite successful, too - my compliments) at starting a flame war, I'll now bow out and retire from it.