hermetic

Hermetic derives from Greek via the Medieval Latin word hermeticus. When it first entered English in the early 17th century, hermetic was associated with writings attributed to Thoth, the Egyptian god of wisdom. Thoth, whom the Greeks called Hermes Trismegistus ("thrice-great Hermes"), was believed to be the author of a number of mystical, philosophical, and alchemistic works. The obscure subject matter of these works may have made them difficult to wade through, for soon English speakers were also applying hermetic to things that were beyond ordinary human comprehension. Additionally, Hermes Trismegistus was said to have invented a magic seal that could keep vessels airtight. Hermetic thus came to mean "airtight," both literally and figuratively. These days, it can also sometimes mean "solitary."