Middle English erthe, from Old English eorþe "ground, soil, dirt, dry land; country, district, the (material) world, the abode of man, 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-, "earth, ground."
