HughM, I see what you mean but there seems to be various "smiths" in Gaelic. For example, a farrier is described as a gobha-"horse-shoe" and another name for a blacksmith is gobha-"iron" so I can only think that gobha is a metal worker who can work with iron but there are special types of work he does. The gobha an duine in the song I would think is merely emphasis (I think!)