the process of turning a historical or semi-historical person or event into a myth

Mysticism (from the Greek μυστικός – mystikos, an initiate of the Eleusinian Mysteries; μυστήρια – mysteria meaning "initiation"[1]) is the pursuit of achieving communion, identity with, or conscious awareness of ultimate reality,...

Euhemerism summary and related information.

hero cult

interpretation of accounts in terms of mythology, see mythography

in particular the term is used for those who have a mythological interpretations of Jesus Christ or deny/doubt his historicity.