Hermes Trismegistus (literally, thrice greatest) was a late name of hermes, especially as identified with the Egyptian god Thoth. He was the fabled inventor of astrology and alchemy.
Originally, a boundary stone dedicated to Hermes as the god of boundaries, and therefore bearing in some cases a head, or head and shoulders, placed upon a quadrangular pillar whose height is that of the body belonging to the head, sometimes having feet or other parts of the body sculptured upon it. These figures, though often representing Hermes, were used for other divinities, and even, in later times, for portraits of human beings. Called also herma. See terminal statue, under terminal.
Origin: L, fr. Gr.