Etymology
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listless (adj.)
"languid and unresponsive, slothful," mid-15c., from Middle English liste "pleasure, joy, delight" (see list (v.4)) + -less. Spenser, if no one else, tried listful (1590s). Related: Listlessly; listlessness.
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moony (adj.)

1580s, "like the moon;" 1848, "dreamy, listless, bewildered," from moon (n.) + -y (2). Also see moon (v.).

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languid (adj.)

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.

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oscitant (adj.)

"sleepy, drowsy, sluggish," literally "yawning, gaping," 1620s, from Latin oscitans "listless, sluggish, lazy," present participle of oscitare "to gape, yawn," from os citare "to move the mouth" (see oral and cite). Related: Oscitancy.

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drift (v.)

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.

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mope (v.)

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.

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tedium (n.)

"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."

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languish (v.)
Origin and meaning of languish
early 14c., "fail in strength, exhibit signs of approaching death," from languiss-, present participle stem of Old French languir "be listless, pine, grieve, fall ill" (12c.), from Vulgar Latin *languire, from Latin languere "be weak or faint" (from PIE root *sleg- "be slack, be languid"). Weaker sense of "be lovesick, grieve, lament, grow faint," is from mid-14c. Related: Languished; languishing.
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heartless (adj.)
Old English heortleas "dispirited, dejected;" see heart (n.) + -less. In Middle English with expanded senses "lacking in courage; foolish; listless; half-hearted; sluggish." Sense of "callous, cruel, wanting in kindly feeling" is not certainly attested before Shelley used it thus in 1816. Literal meaning "lacking a heart, lifeless" (mid-15c.) is rare. Related: Heartlessly; heartlessness. Similar formation in Dutch harteloos, German herzlos.
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bore (n.2)

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]
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