Earth Skills

Tera Family

 * Digital Devil Saga series only earth / seismic elemental family.
 * Generally effective against Zio (electric) elemental unit but nullified by Aereal demons.

general spell

 * Tera, word probably shortened from the Roman Goddess of Earth - Terra, the various name of Earth and Gaia as her Greek counterpart.

specific spell

 * Titanomachia, or Titanomachy, meaning the war of Titans in Greek mythology.

Magna Family

 * Persona series only earth / seismic 地変 elemental family.