dehiscence n.

active word-forming element in English and in many verbs inherited from French and Latin, from Latin de "down, down from, from, off; concerning" (see de), also used as a prefix in Latin, usually meaning "down, off, away, from among, down from," but also "down to the bottom, totally" hence "completely" (intensive or completive), which is its sense in many English words.

As a Latin prefix it also had the function of undoing or reversing a verb's action, and hence it came to be used as a pure privative — "not, do the opposite of, undo" — which is its primary function as a living prefix in English, as in defrost (1895), defuse (1943), de-escalate (1964), etc. In some cases, a reduced form of dis-.

c. 1300, yenen, yonen, from Old English ginian, gionian "open the mouth wide, yawn, gape," from Proto-Germanic *gin- (source also of Old English giwian, giowian, giwan "to request," Old Norse gina "to yawn," Dutch geeuwen, Old High German ginen"to be wide open," German gähnen "to yawn"), from PIE root *ghieh- "to yawn, gape, be wide open." Modern spelling is from 16c. Related: Yawned; yawning.

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."