Nicodemite

A nicodemite, usually a term of disparagement, is a person who is suspected of public misrepresentation of their actual religious beliefs by exhibiting false appearance and concealing true beliefs.

Introduced into 16th century religious discourse, its currency persisted into the 18th century and beyond. It was usually applied to persons of publicly conservative religious position and practice who were thought to be secretly humanistic or reformed. Originally employed mostly by Protestants, it was also later used by Catholics as well.