Proper noun
Trismegistus
The epithet of Hermes, the mythological author of the central text of hermeticism.
Davies (2009:8-9) Around this time the legendary figure of Hermes Trismegistus developed as a conflation of the Egyptian god Thoth and the Greek Hermes ; this figure was associated with writing and magic and, therefore, of books on magic. Source: Internet
The writings attributed to Hermes Trismegistus are a primary source of alchemical theory. Source: Internet