Old English eorþe "ground, soil, dirt, dry land; country, district," also used (along with middangeard) for "the (material) world, the abode of man" (as opposed to the heavens or the underworld), from Proto-Germanic *ertho (source also of Old Frisian erthe "earth," Old Saxon ertha, Old Norse jörð, Middle Dutch eerde, Dutch aarde, Old High German erda, German Erde, Gothic airþa), perhaps from an extended form of PIE root *er- (2) "earth, ground."

The earth considered as a planet was so called from c. 1400. Use in old chemistry is from 1728. Earth-mover "large digging machine" is from 1940.

as an annual ecological awareness event on April 22, from 1970; the idea for it and the name date from 1969.

c. 1600, "firmly fixed in or on the earth," from earth (n.) + bound (adj.). Figurative sense "bound by earthly ties or interests" is from 1869.

also earth-light, "sunlight reflected from Earth's surface and clouds," especially as illuminating the otherwise dark part of the moon, 1810, from earth (n.) + light (n.). Earthshine in same sense is from 1814.

Old English eorþlic "worldly, pertaining to this world" (as opposed to spiritual or heavenly); see earth (n.) + -ly (1). The sense "belonging to or originating in the earth" is from mid-15c.