I believe that 'Mo Ghile Mear' is an Irish Jacobite song but may have been written quite some time after the 'forty five'(1745 Rebellion) in Scotland. I have also seen versions entitled 'Mo Ghiolla Mear' which would have a somewhat different translation. In my youth I knew an old lady who called all children 'A Ghillín', which I think was similar to 'my pet' or 'my darling'. I hope that you won't confine yourself to Sting's version of this great song, Adolfo; estimable though it be, there are many better recordings available in sean nós and more modern styles. Of the latter I like Mary Black's version best.