A person who resembles Nicodemus; a secret or timid adherent; specifically a Protestant living in a Catholic country in the 16th century who concealed his or her faith to escape persecution.
Nicodemus was afraid of being seen with Jesus and visited him at night (John 3:1 ff.).
Late 16th century. From Middle French Nicodemite from post-classical Latin Nicodemus (Vulgate; from Hellenistic Greek Νικόδημος, the name of the Jewish ruler who visited Jesus by night) + Middle French -ite.