hypogean (adj.)

Earth as a goddess, from Greek Gaia, spouse of Uranus, mother of the Titans, personification of gaia "earth" (as opposed to heaven), "land" (as opposed to sea), "a land, country, soil;" it is a collateral form of gē (Dorian ga) "earth," which is of unknown origin and perhaps from a pre-Indo-European language of Greece. The Roman equivalent goddess of the earth was Tellus (see tellurian), sometimes used in English poetically or rhetorically for "Earth personified" or "the Earth as a planet."