A question came up elsewhere about which astronomer first applied the term Earth to the planet, as distinct from the material world. Etymology Online gives a rough date, but no details, which makes me a bit suspicious.
http://www.etymonline.com/index.php?term=earthearth Look up earth at Dictionary.com
O.E. eorše "ground, soil, dry land," also used (along with middangeard) for "the (material) world" (as opposed to the heavens or the underworld), from P.Gmc. *ertho (cf. O.N. jörš, M.Du. eerde, O.H.G. erda, Goth. airža), from PIE base *er-. The earth considered as a planet was so called from c.1400. Earthy in the fig. sense of "coarse, unrefined" is from 1594. Earthworm first attested 1591. Earthwork is from 1633. Earthlight apparently coined 1833 by British astronomer John Herschel.
Anybody know more details about who might have first applied the existant word Earth to the planet?