"uneasy or disturbed state of mind," 1709; from disquiet on model of quietude. Disquietness is from 1530s.
Entries linking to disquietude
disquiet v.
"deprive of peace, rest, or tranquility," 1520s, from dis- + quiet (v.). Related: Disquieted; disquieting. As a noun, "want of quiet, rest, or peace," 1580s.
quietude n.
"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.