hermetic
airtight; occult
Today this word meansSealed so completely that no air passes. Or secretive and arcane.
From "Hermes Trismegistus," the legendary sage of Hellenistic Egypt, created by fusing Hermes with the god Thoth.
Alchemists believed he had taught the art of the perfect seal. "The seal of Hermes" is airtightness itself.