Interesting site, Masato!

Just a detail, but it's mavourneen, not mavoureen, and it's a term of endearment, not part of her name.

According to Sean McMahon, in his wonderful collection of Irish verse, song and prose, Rich and Rare, Kathleen Mavourneen was at one time a euphemism for hire-purchase debt, on account of that repeated phrase "it may be for years, and it may be forever." Anyone else heard it used that way?

He credits the words, correctly it would seem, to Julia Crawford. In a biographical note he says: "Julia Crawford was born Louise Matilda Jane Montague, perhaps in Co Cavan, in 1799. She was the author of many poems and novels, all of which have passed into obscurity except for the ironclad Kathleen Mavourneen. She died in 1860."