"become quiet or calm, become silent," 1821, from Latin quiescere "to rest," from suffixed form of PIE root *kweie- "to rest, be quiet."
"state or quality of being inactive," 1630s, from Latin quiescentia, from quiescere "to rest" (from suffixed form of PIE root *kweie- "to rest, be quiet"). Related: Quiescency.
1630s, "rest, quiet, satisfaction," from French acquiescence, noun of action from acquiescer "to yield or agree to; be at rest" (see acquiesce). Meaning "silent consent, passive assent" is recorded from 1640s.
late 14c., "peaceable, being in a state of rest, restful, tranquil, not moving or agitated," from Old French quiet and directly from Latin quietus "calm, at rest, free from exertion," from quies (genitive quietis) "rest" (from PIE root *kweie- "to rest, be quiet").
From 1510s as "peaceable, not turbulent, characterized by absence of commotion." By 1590s as "making no noise." From 1570s as "private, secret." As an adverb from 1570s. Quiet American, frequently meaning a U.S. undercover agent or spy, is from the title of Graham Greene's 1955 novel. Related: Quietly; quietness.
It forms all or part of: acquiesce; acquit; awhile; coy; quiesce; quiescent; quiet; quietism; quietude; quietus; quit; quitclaim; quite; quit-rent; quittance; requiescat; requiem; requite; while; whilom.
It is the hypothetical source of/evidence for its existence is provided by: Avestan shaitish "joy," shaiti- "well-being," shyata- "happy;" Old Persian šiyatish "joy;" Latin quies "rest, repose, quiet;" Old Church Slavonic po-koji "rest;" Old Norse hvild "rest."
c. 1600, of a letter, "not sounded," from Latin quiescentem (nominative quiescens), present participle of quiescere, inchoative verb formed from quies "rest, quiet" (from suffixed form of PIE root *kweie- "to rest, be quiet"). From 1640s as "resting, being in a state of repose." Related: Quiescently.
"rest, repose, quiet, tranquility," 1590s, from French quiétude (c. 1500) or directly from Late Latin quietudo, from Latin quietus "free; calm, resting" (from PIE root *kweie- "to rest, be quiet"). In the same sense quietness is attested from mid-15c.