Thumbstall

Thumbstall in ecclesiastical nomenclature, is a ring, set with pearls and rubies, or a rich ornament worn by the bishop over that part of the thumb of his right hand which had been dipped in the chrism, or holy oil. This was worn out of respect to the holy oil, and to preserve his garments from stains. It was removed at that part of the service when he washed his hands. This ring was anciently called a "poucer."