Who named the Earth and why "Earth", or in other words what does Earth
mean?  It seems that all the other planets are named for Gods and such
so why is Earth called Earth?

In a strictly technical sense, our planet is called "Earth" because
the International Astronomical Union says so:

"The official names of planets and their moons are governed by an
organization called the International Astronomical Union (IAU)... The
IAU is the internationally recognized authority for assigning names to
celestial bodies and any surface features on them.

The IAU recognizes that astronomy is an old science and many of its
names come from long-standing traditions and/or are founded in
history. For many of the names of the objects in the solar system,
this is especially so. Most of the objects in our solar system
received names long ago based on Greek or Roman mythology. The IAU has
therefore adopted this tradition in its rules for naming certain types
of objects in the solar system... Earth is the only planet whose
English name does not derive from Greek/Roman mythology. The name
derives from Old English and Germanic. There are, of course, many
other names for our planet in other languages."

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question48.html

The word for 'Earth' is not the same in all of Earth's languages. Here
are a few examples:

"Afrikaans: aarde
 Danish: verden
 Finnish: maa
 French: mondiale
 German: Erde
 Indonesian: dunia
 Japanese: tsuchi, yochi, chi, a-su, daichi, koudo
 Russian: çåìë
 Swahili: kiwanja
 Swedish: mull"

The Straight Dope Archives: Do other languages call Earth "Earth"?
http://www.straightdope.com/mailbag/mearth.html

Here you'll find an interesting table that lists the names of the Sun,
the Moon, the Earth, and the other planets of the Solar System in many
different languages:

Students for the Exploration and Development of Space: Planetary
Linguistics
http://www.seds.org/billa/tnp/days.html

"Some other names for 'Earth' are; 

 Aztec: Coatlicue 
 Chinese: Hou ji 
 Danish: Jorden 
 Dutch: Aarde 
 Egyptian: Geb 
 Estonian: Maa 
 French: Terre 
 German: Erde 
 Greek: Gaea 
 Hebrew: HaOlam 
 Incan: Pachamama 
 Italian: Terra 
 Japanese: Chikyuu 
 Latin: Terra 
 Maltese: Dinja 
 Maori: Papa 
 Mayan: Bacabs 
 Norse: Midgard 
 Norwegian: Jorden 
 Polish: Ziemia 
 Portuguese: Terra 
 Russian: Zemlya 
 Serbo-Croatian: Zemlja 
 Slovene: Zemlja 
 Spanish: Tierra 
 Sumerian: Enlil 
 Icelandic: Jör<eth>in 

The Earth has often been personified as a deity, often a goddess. See
Gaea and Mother Earth. In Norse mythology, Earth was the son of Nott
and Annar."

Internet Encyclopedia: Earth
http://www.internet-encyclopedia.info/wiki.phtml?title=Earth

"earth - 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."

Online Etymology Dictionary
http://www.etymonline.com/e1etym.htm

"The name of our planet is the Earth. The name of our moon is the
Moon. The name of our solar system is the Solar System.

Notice that I capitalize them, because when used as names, they are
proper nouns. This also helps us distinguish between the planet Earth
and earth (meaning soil), between the Earth's Moon and moon (meaning
the natural satellite of a planet), and between our Solar System and
any other solar systems (since any system containing a star and a
planet or a planet-forming disk can be called a solar system.)

This is the usage approved by the International Astronomical Union,
the body in charge of naming celestial objects... You may read or hear
people using Luna for the Moon, or Terra or Gaia for the Earth, or Sol
for the Sun, but these are poetic terms, often seen in science fiction
stories, but not used by astronomers in scientific writing."

Cornell University: Ask an Astronomer
http://curious.astro.cornell.edu/question.php?number=289

One thing to keep in mind is that only recently has there been
widespread acceptance of the fact that Earth is a planet, very much
like other planets such as Mars and Venus. For most of mankind's
history it was believed that Earth was the hub of everything,
including the Solar System. All the Universe was thought to center
upon our world. The planets that were seen in the sky were recognized
to be something different from the stars, since it was observed that
their motions were not like the stars' motion in the night sky.

The ancient Romans were aware of five planets. They named them after
some of their most important gods: Mercury (Messenger of the Gods),
Venus (Goddess of Love), Mars (God of War), Jupiter (King of the Gods)
and Saturn (God of Time and the Harvest). In later years, the
tradition of giving the names of Roman deities to planets was
continued by astronomers as new planets were discovered.

Our word "planet" comes the Greek "planetes," meaning "wanderer," in
observation of the fact that the planets seemed to "wander" among the
fixed stars. The idea that Earth, too, was a "wanderer" was
counterintuitive, and was viewed by many as a religious heresy. In the
third century B.C., the Greek philosopher and mathematician
Aristarchus of Samos postulated that the Earth was a planet, and that
it revolved around the sun. Many centuries later, in 1543,
Aristarchus's ideas were more successfully presented by Copernicus.

"Earth:  Terra (Gaea); Erd (German)  
In Classical mythology, the Earth was called Terra Mater or Tellus by
the Romans and Gaea by the Greeks. Both names mean Earth. Gaea was the
daughter of Chaos and she married her own son Uranus. Terra or Gaea
was the mother of the Titans, including Saturn (Cronus). However, the
name we use today was named after the ancient German goddess named
Nertheus or Erd; they are probably two different goddesses."

Timeless Myths: Classical Mythology
http://www.timelessmyths.com/classical/stars.html

"Who named our planet 'earth?' 

We do not know, and I do not think there is really any way of
knowing... In English, 'earth' has been only recently (a few
centuries) used for the planet -- 'world' becomes more common the
further back you go. But 'earth' has been used for ground or soil much
longer. 'earth' is also obviously and closely related to the German
'Erde' which has a similar and probably longer usage for both planet,
ground, and soil.

When language gradually changes like this, and especially when a word
is old, and has related forms in other languages, its use can seldom
be traced back to a single 'namer' or 'inventor'."

MadSci Network: Earth Sciences 
http://www.madsci.org/posts/archives/nov2001/1004895905.Es.r.html 

"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."

So, as with the names of the other planets that have been known
throughout human history (Mercury, Venus, Mars, Jupiter and Saturn),
it's difficult to say who first thought of the planet as Earth. The
names were part of culture even before we really understood the
significance of what planets are and where they are in space."

Cornell University: Ask an Astronomer 
http://curious.astro.cornell.edu/question.php?number=451 

"The true origin of the word Earth is shrouded in history and so any
individual responsible for it cannot be found.

There are actually two schools of thought as to the origin of the word
Earth. One was the already mentioned varitaion of the Germanic
'ertho'. The other is that it originated from the Indo-European "er",
the verb form of which is 'ar', meaning 'to plough'.

The later, however, is not generally considered as likely due to the
Germanic version contains more of the same letters and so indicates a
natural progression. However, it would still be likely that the
Germanic word would itself be derived from the Indo-European."

Cached copy from ABC.net Forums Science Archive: Who Named Earth?
http://web.archive.org/web/20020806232116/http://www2b.abc.net.au/science/k2/stn-old/archive2001/posts/November/topic504399.shtm

"The word 'earth' is from old germanic roots meaning 'the ground' and
extended to the ground we live on between heaven and hell. The planets
were recognised from their appearance in the night sky and were named
different things by different cultures. In English, we followed the
conventions of the Romans in planet naming but stuck with our germanic
past for the Earth, rather than the Latin terra. Once we realised that
we were in fact on a planet orbiting the sun, the name for our home
area, earth, was extended to the planet. This is purely a convention
in the English speaking world. Other languages call it other things.
Interestingly, those cultures that have their own names for the
planets still accept the standard names ( Mercury, Venus, Mars etc and
all accept Uranus, Neptune and Pluto as these cannot be seen by the
naked eye and were named by their discoverers) but very few use
anything but their own local name for the planet we live on. It is
part of the culture."

ABC.net Forums Science Archive: Naming Earth
http://www2.abc.net.au/science/k2/stn-archive1/posts/topic40587.shtm

Search terms used:

"the word earth"
"the name earth"
"named earth"
"naming earth"
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"earth's name"
"earth" + "planets" + "roman"

Many thanks to my good friend and colleague bobbie7-ga, who provided
some of the source material linked above.

I hope this information is helpful. If anything is unclear, or if a
link doesn't function, please request clarification; I'll be glad to
offer further assistance before you rate my answer.

Best regards,
pinkfreud

A quick comment to Pink's most erudite response, with respect to the
Ancient Egyptian terminology

Geb is the the name of the Ancient Egyptian earth god, who was
separated from his beloved Nut (goddess of the sky), through the
action of Shu, god of air.

However, the Egyptians also used the word "ta" to mean earth, in
opposition to "pet" meaning sky.  "Ta" also meant land, as in the
compound word "ta-mera", beloved land, which was one of their names
for Eygpt.
You can see the hieroglyph for ta at
http://www.touregypt.net/historicalessays/hyrotutor/learninghieroglyphs3.htm
(it loads very slowly)

why did all the other planets get good names?  'earth' means 'dirt'.

Most people thought until relatively recently that the Earth was not a
'wandering' planet, it was permanently stuck in the firmament, other
planetary bodies moved around.

The question of roundness and motion are related, but similiar.

The educated knew the Earth rotated around the earth but not the
masses, who were largely peasants who could not read or write and were
little concerned about the roundness, flatness or movement of the
earth. Galileo and Copernicus knew of course. I remember a cartoon on
a professor's office door with Galileo talking about planetary orbits
and council members wondering what the words "planetary" and "orbit"
meant. Religious leaders were not always at the forefront of
scientific knowledge in those days. Just like George Bush, president
of the United States, leaders are sometimes as uninformed as the
masses who vote for them.

So that would make sense why many people believe today that
Christopher Columbus sailed to prove the Earth was not flat, which he
did not. To show the council in Spain he was right and they were
wrong. The educated and Columbus knew the world was round in 1492,
they were not sure of the size of the earth and whether Columbus could
make it there and back to Cathay-China in the little ships available
for sailing.

This is a significant misunderstanding about Columbus and it relates
to the new knowledge that was developing at the time and it was not
learned by everyone at the same time. There are millions who believe
the universe was made in seven days. And I read in the Economist
magazine a while back, about half of Americans do not know the earth
rotates around the sun.

There are web pages railing at the misunderstanding the mass media has
about Columbus' voyage, the name of the Earth and how recent
scientific ideas have not yet been entirely clarified yet. Europe
found out about America when scientific knowledge was just in its
infancy and a few key points still need to be ironed out it seems.