Thanks for re-opening the debate Greg - I was amazed at the response previously to such a simple question, but it looks like no-one has anything new to add.

So I guess the creation of the distinctive Manx names was not a deliberate act by our Lancastrian rulers to reduce the Scottish/Irish influence by making the use of the Mac prefix illegal, in a similar move to anti-Gaelic actions in Ireland at around this time, but rather a natural shortening of the 'new' patronymic surnames through continual verbal use and their subsequent recordal in official records.

It is a shame that our surname origins seem to have come about through linguistic laziness rather than a more romantic history of persection - no source of righteous indignation here then!