*ghieh-

late 14c., "gaping void; empty, immeasurable space," from Old French chaos (14c.) or directly from Latin chaos, from Greek khaos "abyss, that which gapes wide open, that which is vast and empty" (from *khnwos, from PIE root *ghieh- "to yawn, gape, be wide open").

The meaning "utter confusion" (c. 1600) is an extended sense from theological use of chaos in the Vulgate version of "Genesis" (1530s in English) for "the void at the beginning of creation, the confused, formless, elementary state of the universe." The Greek for "disorder" was tarakhē, but the use of chaos here was rooted in Hesiod ("Theogony"), who describes khaos as the primeval emptiness of the Universe, and in Ovid ("Metamorphoses"), who opposes Khaos to Kosmos, "the ordered Universe." Sometimes it was personified as a god, begetter of Erebus and Nyx ("Night").

Meaning "orderless confusion" in human affairs is from c. 1600. Chaos theory in the modern mathematical sense is attested from c. 1977.

1590s, "deep crack in the earth," from Latin chasma, from Greek khasma "yawning hollow, gulf," related to khaskein "to yawn," and thus to chaos. In English in 17c. often spelled chasma. Figurative use, in reference to a great interruption or wide breach of any kind, is from 1640s. Related: Chasmy (1786); chasmal (1842, Poe); chasmic (1885). The bloody chasm (1868) was an old rhetorical phrase for the American Civil War.