I tend to agree with Malcolm Douglas here. The 18th century musical play "Fish for me cash", and the 17th century tune "Island Field", that are the suggested sources of "Danny Boy" sound suspiciously like fabrications to me. Lets have some references to this before we pass this information on! I would love to believe it, it's such fun to trace tunes back hundreds of years through various versions, but it's always as well to have a pinch of salt handy.