Chaos

Chaos (Ancient Greek: Χάος Kháos) was the first of the protogenoi, and represented the primeval void that preceded all of creation in Greek mythology. Although the English word "chaos," meaning, "complete disorder and confusion," is derived from the word Kháos, this did not reflect the ancient Greek understanding of the deity, and was a product of later associations by late-classical authors who viewed Chaos was a turbulent mixture of the elements.

Etymology
Chaos comes from the Greek word χάος (Kháos), which means "emptiness, vast void, chasm, abyss," and also from the verb χαίνω (kháskō), which means "gape, be wide open." Both terms derive from the Proto-Indo-European *ghen-, a cognate to the Old English "geanian," which means "to gape" or "to yawn."

Chaos in Ancient Greek Sources
To the ancient Greeks, Chaos referred to the void that existed prior to the creation of the cosmos, as well as the lower atmosphere that exists between the earth (Gaia) and the upper heavens (Aeither and Ouranos) post-creation. Chaos, like other protogenoi, was not typically thought of in personified terms, but was often referred to in the feminine.

Hesiod's Theogony
In Hesiod's famous work, the Theogony, the origin of the cosmos and the gods is described. According to Hesiod, Chaos was the original state of existence through which all things can trace back their ancestry- with Gaia (earth), Tartaros (the pit beneath the earth), Eros (Love), Erebos (Darkness), and Nyx (Night) being Khaos' direct offspring:

"First it was Chaos, and next broad-bosomed Earth, ever secure seat of all the immortals, who inhabit the peaks of snow-capped Olympus, and dark dim Tartaros in a recess of Earth having-broad-ways, and Eros [Love], who is most beautiful among immortal gods, Eros that relaxes the limbs, and in the breasts of all gods and all men, subdues their reason and prudent counsel. But from Chaos were born Erebos and black Night; and from Night again sprang forth Aether and Day, whom she bore after having conceived, by union with Erebos in love."

- - Hesiod, Theogony, 8th Century BCE (Translated by J. Banks)

Chaos in Ancient Roman Sources
To the ancient Romans, Chaos was not thought of as a void, but instead a chaotic churning mixture of all the elements (Earth, Fire, Water, and Wind). This notion of Chaos influenced the typical modern English usage of the word.

Ovid's Metamorphoses
Ovid was a famous Roman poet who lived sometime around the first century BCE until sometime around the first century CE. His most famous work was his retelling of Greek myths, called "Metamorphoses," since each story in the collection revolves around the idea of some sort of transformation. Ovid describes the transformation of Chaos into cosmos in the beginning of the first book of Metamorphoses:

"Before there was earth or sea or the sky that covers everything, Nature appeared the same throughout the whole world: what we call chaos: a raw confused mass, nothing but inert matter, badly combined discordant atoms of things, confused in the one place. There was no Titan yet, shining his light on the world, or waxing Phoebe renewing her white horns, or the earth hovering in surrounding air balanced by her own weight, or watery Amphitrite stretching out her arms along the vast shores of the world. Though there was land and sea and air, it was unstable land, unswimmable water, air needing light. Nothing retained its shape, one thing obstructed another, because in the one body, cold fought with heat, moist with dry, soft with hard, and weight with weightless things This conflict was ended by a god and a greater order of nature, since he split off the earth from the sky, and the sea from the land, and divided the transparent heavens from the dense air. When he had disentangled the elements, and freed them from the obscure mass, he fixed them in separate spaces in harmonious peace. The weightless fire, that forms the heavens, darted upwards to make its home in the furthest heights. Next came air in lightness and place. Earth, heavier than either of these, drew down the largest elements, and was compressed by its own weight. The surrounding water took up the last space and enclosed the solid world."

- -Ovid, Metamorphoses, 1st Century BCE (Translated by A. S. Kline)