All McGaffin researchers should also have a look at the 'McGuffin' message board because it is certain McGaffins and McGuffins are the same family. My ancestors were McGuffins and I have come across registers with their name spelled McGaffin.
It appears all or most Mcguffins came from Newry and Dungannon in Northern Ireland, and they were a part of the Ulster Plantation with origins from Scotland.
Please view the 'McGuffin' message board on this site and also on Genforum: http://genforum.genealogy.com/mcguffin/
There are many messages already posted and you are sure to find a connection somewhere.