In 1453, Constantinople fell to the Turks; for two centuries more, Europe faced an Ottoman Empire that threatened to conquer Vienna and spill into central and western Europe. But as Byzantine refugees fled into Europe, they brought with them their scholarship, helping to spur the Italian Renaissance forward, particularly with their translations of (and abiding interest in) Plato. But they brought something else with them: the Corpus Hermeticum. These books were the works of Hermes Trismegistus, contemporary of (or perhaps even precursor to!) Moses and greatest magician of the age, Hermes the Triple Master, Hermes Thrice-Great. The Corpus Hermeticum "landed like a well-aimed bomb amid the philosophical systems of late medieval Europe". It fit in neatly among the esoteric traditions of Europe; alchemy, studied by European scholars from Roger Bacon in the thirteenth century to Isaac Newton in the eighteenth, was perhaps at its peak. And if Hermes Trismegistus was approvingly cited by pillars of the early church and classical scholars, if his philosophy was so influential on these revered men, surely the alchemy of his scholarly descendants was acceptable to the modern church? This neat argument was, unfortunately, premised on two mistakes: the Corpus Hermeticum did not date back to the time of Moses (it was a much later work, probably Egyptian, and was not so much influential upon important church documents as influenced by them), and there was no Hermes Trismegistus.
The name "Hermes Trismegitus" was not unknown in Europe before the revival of the Corpus; a number of other works were attributed to him (the ill-defined boundaries of a manuscript made it easier for this to occur, and discrepancies in the timeline could be neatly explained by saying that later manuscripts were translations of lost earlier works), and he was known to earlier scholars such as Thomas Bradwardine. But although the idea of Hermes Trismegistus lingers on in contemporary mystical traditions (the English translation of the Corpus available online was written by a twentieth-century follower of Blavatsky), contemporary scholarship dates the Corpus Hermeticum to a group of Egyptian manuscripts from the third or fourth century A.D. They were collected into a single volume well before they fell into the hands of Lorenzo de Medici‘s agents; the Duke of Tuscany had it translated into Latin by the Neoplatonist Marsilo Ficino, and from there it spread like wildfire.
The name Hermes Trismegistus seems to have been assigned in antiquity to the presumed single author of the Corpus Hermeticum. Was it simply out of respect? Hermes was the Greek god of writing and thieves; he is associated by some mystical traditions with Thoth, the Egyptian god who was said to have invented hieroglyphics (leading slowly but inevitably to his appearance as a recurring motif in the work of Jacques Derrida). Hermes Trismegistus was a Greco-Egyptian amalgam of Hermes and Thoth.
Invented and mistaken authorship for alchemical publications seem to have been relatively common. Geber, the fourteenth-century author of Summa perfectionis magisterii ("The Perfect Mastery") and Liber fornacum ("The Book of Furnaces") is also known as the "False Geber". The false Geber, thought to be a Spaniard, had assumed the name of an eighth-century Arab alchemist, Jabir ibn Haiyan, whose works had been translated into Latin centuries earlier. The false Geber was ahead of his time:
We find in them [Geber’s writings] remarkably sound views on methods of chemical research; a theory of metals (the six metals differ essentially because of different proportions of sulfur and mercury in them); preparation of various substances (e.g., basic lead carbonate; arsenic and antimony from their sulfides). Geber deals also with various applications, e.g., refinement of metals, preparation of steel, dyeing of cloth and leather, varnishes to water-proof cloth and to protect iron, use of manganese dioxide in glass-making, use of iron pyrites for writing in gold, distillation of vinegar to concentrate acetic acid. He observed the imponderability of magnetic force.
Of course, maybe he had help, as "the study of the manuscripts and printed texts of Geber suggests that the corpus of the writings attributed to Geber is not the work of a single man but, rather, that of a school."
Choosing a name that harkened back to one of the fathers of alchemy was well and good, but Geber discovered sulphuric acid, perhaps the single most important chemical discovery between the classical age and the development of modern science. He (or they, or she) missed a crucial opportunity to crow. After all, even if he did eventually become patron saint of natural scientists, Albertus Magnus, "Doctor Universalis", surely didn’t get named "Albert the Great" by his parents.