Abbot is so short and squared off at the end that it is hard to make another word that is shaped and weighed the same.

Carist (the most caring of the hospital => care-est => carist)
Loreot (lore + abbot; plays on the sound of "laureate")
Magischar (sort of like "Mage Chairman")

Are you going for something that sounds like it should be English, or something accented?