quiescent (adj.)

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.