"pertaining to the earth," 1846, from -ian + Latin tellus (genitive telluris) "earth, land, ground; the earth" (related to Tellus, Roman goddess of the earth), from PIE root *tel- "ground, floor" (cognates: Lithuanian telinat "spread out, flat," Sanskrit talam "plain, sole of the foot," Old Church Slavonic tilo "floor," Greek telia "dice board," Old Irish talam "earth," Old Norse tilja, Middle Dutch dele "plank"). As a noun, "inhabitant of Earth" (with reference to supposed inhabitants of other worlds) from 1847.