reiver - as far as my fairly wee knowledge of the languages goes:

there are irish and scottish gaelic dialects, with a fair few differences, but overall a similar sound. i believe the irish language was "modernised" in the 50s and a few of the words were made a lot smaller, whilst scottish gaelic was left alone. but the lowland scottish dialect is called scots, and is more like a very colloquial version of english.