From “Mystery, Myth, and Magic” (by A.A.Barb)
With Hermes Trismegistus we seem to get somewhat nearer to genuine ancient Egypt. For the Egyptians the god Thoth was the inventor of all science, the guardian of the secrets of past and future, not least the master of the magic arts. Plato already wrote about him (Phaedrus, 274cf.; Philebus, i8bf.) as the ‘father of letters’, transcribing his name as ‘Theuth’. Thoth was also the helper of the dead. All this suggested to the Greeks (and the Romans) an identification with their Hermes (or Mercurius). Later speculation made him one of several of this name, the ‘thrice greatest’ Hermes (a clumsy translation of an actual Egyptian attribute) who in some treatises was introduced as writing to his son ‘Tat’ (obviously = Thoth). Numerous books went under his name; the late Neoplatonic philosopher Iamblichus mentions in his work on the Egyptian mysteries (viii. i) astronomical numbers (20,000, 36,525) alleged to have been written by him. There may really have been Egyptian books claiming this authorship, but the Hermetica which were handed down to us obviously originated in Roman Imperial times, most probably between A.D. 150 and 300. Details of an astrological, alchemical, or magical nature which they contain might be derived from ancient Egyptian tradition. But their main body of mystic-theosophical philosophy seems pure late-Hellenistic, anti-rationalistic syncretism typical of late antiquity, although set in Egyptian scenery and presented by pseudo-Egyptian personalities. One might almost draw a parallel with the Magic Flute, where contemporary Freemasonry similarly paraded its pretended antiquity in an old-Egyptian setting. However, like Horapollo’s Hieroglyphica, the Corpus Hermeticum also was taken at its face value (already by the Latin Fathers of the Church) and Hermes Trismegistus was accepted as the great prophet of remote antiquity, slightly younger, if not even older, than Moses, and at any rate much older than Pythagoras, Orpheus, or Plato, who all learned from him. When Greek manuscripts began to arrive in Renaissance Florence of the fifteenth century, the Hermetica were given precedence in being hurriedly translated into Latin while the works of Plato took only second place.
— Quoted from: The Legacy of Egypt (edited by J.R.Harris) – Oxford University Press 1971; “Mystery, Myth, and Magic” (by A.A.Barb)