In George F. Black's book "The Surnames of Scotland", it is said that the name "McGimpsey was Irish and derived from MacDiomsaigh, a Gaelic form. MacDiomsaigh, son of Diomasaigh, meaning proud" In Woulf's book "Irish Surnames", it is said that the name McGimpsey is remarkable because of the close concentration of the name in one small area around Newtownards County Down, Ireland, where it is quite numerous.
I will send you ID and Password to "jlmcgimsey.com" The oblong red that has "Welcome" click on it and read various family origins.However I think the above is the most probable origin. They all could be true since they have differenct periods of time. I do believe we may be descendants of Vikings also.
I think you are already a member of Myfamily .com but if you have lost the ID and Password let me know and new ones will be sent.