1590s, from French languide (16c.) and directly from Latin languidus "faint, listless, and sluggish from weakness, fatigue, or want of energy," from languere "be weak, be fatigued, be faint, be listless," from PIE *langu-, from root *sleg- "be slack, be languid." Related: Languidly; languidness.
late 16c., "to float or be driven along by a current," from drift (n.). Transitive sense of "to drive in heaps" is from 1610s. Figurative sense of "be passive and listless" is from 1822. Related: Drifted; drifting. To drift apart "gradually lose mutual affection" is by 1859.
1560s, "to move and act unconsciously;" 1580s, "to be listless and apathetic," the sound of the word perhaps somehow suggestive of low feelings (compare mop (v.) "make a wry mouth" (1560s); Low German mopen "to sulk," Dutch moppen "to grumble, to grouse," Danish maabe, dialectal Swedish mopa "to mope"). Related: Moped; moping; mopey; mopish.
"tediousness," 1660s, from Latin taedium "weariness, irksomeness, disgust" (mostly post-classical), which is related to taedet "it is wearisome, it excites loathing" (in Late Latin "be disgusted with, be weary of") and to taedere "to weary," but the whole group is of uncertain etymology. Possible cognates are Old Church Slavonic težo, Lithuanian tingiu, tingėti "to be dull, be listless."
1778, "thing which causes ennui or annoyance by dullness;" earlier "state of boredom, fit of listless disgust" (1766); of persons who cause boredom by 1812; usually said to be a figurative extension of bore (v.1) on the notion of "move forward slowly and persistently," as a boring tool does, but OED has doubts and early evidence suggests a French connection.
Le secret d'ennuyer est celui de tout dire (The secret of being a bore is to tell everything) [Voltaire, "Sept Discours en Vers sur l'Homme," 1738]