A question of accent?

Generally speaking the variations of our clan name can be divided either by the first vowel following 'Mc' or by the last vowel of the name. The first distinction appears to give us an evolution from 'E' to 'I' and we can probably account for this as a modest change in accent as the clan moved from Scotland to Ireland. The evolution of the last vowel may be accounted for by the same process, that is the change from 'o' to 'a'. Thus, putting the two parts of the evolution together, though they may not have happened at the same time, we have the shift from what may be its earliest form in Scotland, namely McElhago to its latest form in Ireland, McIlhagga. It seems to me that all other variants, which have been many, are secondary to these.