I do not know how to begin this, but I will qualify this by offering up a pint to any great answers- on my first trip to the Isle in Feb.!
I am a St.John, and it has been of oral tradition that this family was from the Isle. It was offered to me that our immigrant ancestors' family was from Kirk German which I know now, is the place of the Royal Chapel of Tynwald as well as a town bearing the same name. My family arrived in America in 1634, and was born in 1604. The Royal Chapel was constructed in 1557,and it has been said that they either worked on the Chapel/ and or lived in the town, when they left for America via England, they took the name of the town with them.
I know that many immigrants took their town name/occupation as a surname, but does this sound far fetched? I won't even ask if there is a connection to your families or I'd be buyin' the lot of you a pint!