St. Tibba, or according to some St. Ebba, was an English missionary in the seventh century.
Legend has it that St. Tibba, or it may have been St. Ebba, in the seventh century, had a dream. As a result of it she caused a well to be dug at a spot on Sodor's south west coast, and with its water effected many remarkable cures. The town of Wellsworth would eventually grow up around the well.
The Order of the Poor Clares would eventually establish a Nunnery next to the well, and built a hospital dedicated to St. Tibba around the well, using the supposed holy water from St. Tibba's well to help cure patients. St. Tibba's Hospital now has the highest reputation of any medical facility on the Island.