The word "geode" comes from the Greek word "geōdēs," which means "earth-like" or "earth-shaped." This is a fitting name for these naturally occurring rock formations, as they often contain cavities filled with crystals that resemble miniature versions of the earth's interior.

Here's a breakdown of the etymology:

* geōdēs (Greek): meaning "earth-like" or "earth-shaped"

* geō- (Greek): meaning "earth"

* -dēs (Greek): meaning "like" or "shaped like"

The term was first used in the 18th century by mineralogists to describe these intriguing rock formations.