Can't help with the lyrics but here is some information on Katherine Tynan. She was born in Dublin in 1861 and married her husband H.A. Hinkson in 1883. He was a resident magistrate in Co. Mayo. He died in 1919. She died in 1931. The air of Danny Boy/The Londonderry Air are based as far as I can recall on an old Irish folktune "Maidin I' mBeara." Mike