An Etymological Dictionary of Astronomy and Astrophysics

A combining form meaning “the earth,” used in the formation of compound words.

Etymology (EN): Geo-, form Gk. ge “earth, land, ground, soil.”

Etymology (PE): Zamin, zami “earth, ground,” from Mid.Pers. zamig “earth;”
Av. zam- “the earth;” cf. Skt. ksam; Gk. khthôn, khamai “on the ground;” L. homo “earthly being” and humus “the earth” (as in homo sapiens or homicide, humble, humus, exhume);
PIE root *dh(e)ghom “earth.”