chasm (n.)

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.

Proto-Indo-European root meaning "to yawn, gape, be wide open." 

It forms all or part of: chaos; chasm; dehiscence; gap; gasp; gawp; hiatus; yawn.

It is the hypothetical source of/evidence for its existence is provided by: Sanskrit vijihite "to gape, be ajar;" Greek khainein, Latin hiare "to yawn, gape;" Old Church Slavonic zinoti "to open (one's mouth);" Russian razinut', Serbo-Croatian zinuti, Lithuanian žioju, žioti, Czech zivati "to yawn;" Old English ginian, gionian "open the mouth wide, yawn, gape," Old Norse gina "to yawn," Dutch geeuwen, Old High German ginen "to be wide open," German gähnen "to yawn."