From a local folkie radio show, I got the following on Danny Boy (the DJ was trying to explain why he was playing such a "done to death" song): It was written during World War One by a father whose son died in the war.

BTW the version they played was by De Dannaan, very good in my opinion. I've liked the song since I was a kid and heard it on Harry Belafonte's Carnegie Hall album, and I somehow missed all the soppy versions that made everyone hate it.