why is this planet called earth?

The etymology of earth is:

O.E. eorðe "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. jörð, M.Du. eerde, O.H.G. erda, Goth. airþa), 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.

Earth is also known as Tera.

Unfortunately, I think it's pretty impossible to say exactly who first named the planet 'Earth'. Actually, I really doubt one person really named it intentionally; rather it developed over time as part of the English language. Earth is Old English and German in origin, related to the Old Saxon 'ertha', the Dutch 'aerde', and the German 'erda'. Terra is a French and Latin word, and so isn't part of the 'Earth' etymology. I'm not really an expert on words and word origins, but it seems likely that people used Earth to mean 'land' and then it was the natural thing to refer to all the land and the planet. I tried to look up more specific details about the specific usage of the word over time, but even the Oxford English Dictionary (online) admits:

"Men's notions of the shape and position of the earth have so greatly changed since Old Teutonic times, while the language of the older notions has long outlived them, that it is very difficult to arrange the senses and applications of the word in any historical order."

The name Earth was derived from the Anglo-Saxon word erda, which means ground or soil. It became eorthe in Old English, then erthe in Middle English. The standard astronomical symbol of the Earth consists of a cross circumscribed by a circle.

from

http://en.wikipedia.org/wiki/Earth

The word Earth originates from the Middle English word, erthe, which came from Old English eorthe; akin to Old High German erda. This then traces

back to the Greek, eraze from the Hebrew erez, meaning ground.

Definition

Earth (PLANET) Hide phonetics

noun [S or U]

the planet third in order of distance from the Sun, between Venus and Mars; the world on which we live:

The Earth takes approximately 365&fr14; days to go round the Sun.

The Circus has been described as the greatest show on earth (= in the world).

lol, earth is another word for land example:soil

example:water and h2o

so naturally someone could have wanted to call earth another name like: anything he wanted or she wanted

but that would of started a world war so everyone naturally called earth, earth as is represents land.

It just grew from an expression regarding the ground. Firing arrow fall towards the earth or ground. Other civilizations use different names such as Terra but Earth stuck.

The origin of this word is extraterrestrial. This colony was originally named plxzinrusdk. This is a loose translation of the hubvxus' language of Planet X. You will understand more in 2012 when they return.

Don't know who named it but is possibly called earth because its' crust is made up principally of dirt [earth] whereby people can grow food.