I do not see any connection between Tir Eoghan ( John's territory)and Clan Eoghan(Johns tribe) except the name Eoghan - a widely used name in old ireland, I would assume. But I did enjoy the banter over the origins of a lovley song (and air). This is the type of conversation that should be had in an Irish pub - It would be worth the airfare and the accomodation cost for the experience. The Irish could get their collective teeth into this one - enough to fill a book and a few winter's evenings in front of a turf fire and a pint or three.
    It is one of the things we Irish do better than anyone else on this old mudball.