There's something a bit ironic about the fact that the most fundamental common ground between every human being on the planet is, well, the planet we share--yet nearly every language has its own name for it and a reason why it's such. In English, of course, our planet is Earth--but it's terra in Portuguese, dünya in Turkish, aarde in Dutch. Just imagine the cosmic comedy that would ensue if some interstellar traveler ever stopped on our planet to get directions.
But as diverse as these names are, they all reflect an older worldview--a time before anyone knew our planet was just a fertile sphere floating in the vast darkness of space.To better understand how our planet was regarded historically, it's important to remember that the world was generally regarded as merely the 'setting' of existence and not so much a specific place. In fact, the word 'world' itself didn't originally connote the planet at all, but rather the 'state of human existence'. Germanic in origin, 'world' is a fusion of two now obsolete words translating literally to "age of man."
In this worldview, the elements that made up existence were categorized quite broadly as the Classical elements of Water, Air, Fire, and Earth. Our term 'Earth', consequently, is derived from a much older word which meant simply 'the ground', or 'the opposite of the sea'--much the way the word 'earth' can be used today. These early words for earth, in turn, are references to the Norse goddess Jörð, mother to Thor.
Of course, throughout history, great thinkers in cultures and civilizations throughout the world theorized as to what form was made up of all this earth, with theories of a flat earth reigning supreme up until relatively recently. Early astronomers noted the presence of other planetary bodies and named them after their deities, though our planet kept its connection to the 'soil'--or in Latin terra.
In the fifteenth century, as intellectuals began to reconsider our planet's shape and position in the Universe, the word 'Earth' first came to be used in reference to the planetary body we know it as today and the term considered comparable to Mars, Venus, Saturn, and the other spheres of space.
But despite these early astronomers and mathematicians deducing that Earth was just a planet and not the whole of existence, the notion didn't truly hit home until some time later. Photographic evidence of our round, blue planet Earth didn't appear until the 1950s. Later photos, like "Earthrise" would confirm to the world what we all know now--that Earth is a fragile ecosystem in the cold, vastness of space.
And despite all the different names it's known by, it's home to us all.