late 14c., "of or pertaining to the earth," with + -al (1) + from Latin terrestris "earthly, of the earth, on land," from terra "earth" (from PIE root *ters- "to dry"). Originally opposed to celestial; natural history sense of "living on land" is attested from 1630s. The noun meaning "a human being, a mortal" is recorded from 1590s.