Etymology
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insensible (adj.)
c. 1400, "lacking the power to feel with the senses, numb, dazed" (now rare in this meaning), from Late Latin insensibilis "that cannot be felt," from in- "not" (see in- (1)) + sensibilis "having feeling: perceptible by the senses" (see sensible). Meaning "void of feeling, not susceptible to emotion or passion" is from 1610s. Meaning "incapable of being felt or perceived by the senses or the mind, so small or slight as to be imperceptible" is from late 14c. Compare insensate.
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insensibly (adv.)
"so as not to be felt or perceived," early 15c.; see insensible + -ly (2).
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insensibility (n.)
late 14c., "absence of physical sensation, numbness," from Late Latin insensibilitas, from insensibilis "that cannot be felt" (see insensible). Meaning "quality of being imperceptible" is from 1630s. Meaning "absence of moral feeling, indifference" is from 1690s.
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insensate (adj.)

1510s, "lacking or deprived of physical senses," from Late Latin insensatus "irrational, foolish," from in- "not" (see in- (1)) + sensatus "gifted with sense" (see sensate).

Meaning "irrational, maniacal, lacking or deprived of mental sense" is from 1520s; meaning "lacking or deprived of moral sense, unfeeling" is from 1550s. Insensate means "not capable of feeling sensation," often "inanimate;" insensible means "lacking the power to feel with the senses," hence, often, "unconscious;" insensitive means "having little or no reaction to what is perceived by one's senses," often "tactless." Related: Insensately; insensateness.

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analgesia (n.)
"absence of pain, incapacity of feeling pain in a part, though tactile sense is preserved," 1706, medical Latin, from Greek analgesia "want of feeling, insensibility," from analgetos "without pain, insensible to pain" (also "unfeeling, ruthless"), from an- "not" (see an- (1)) + algein "to feel pain" (see -algia). An alternative form is analgia.
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stolid (adj.)

c. 1600, back-formation from stolidity, or else from French stolide (16c.), from Latin stolidus "insensible, dull, slow, brutish, rude, stupid," properly "unmovable," related to stultus "foolish," from PIE *stol-ido-, suffixed form of root *stel- "to put, stand, put in order," with derivatives referring to a standing object or place.

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marble (adj.)

late 14c., "consisting of marble," from marble (n.). Meaning "mottled like marble" is mid-15c. The earlier adjective in this sense was marbrin (early 14c.). From 1590s as "resembling marble in some figurative quality" (cold, hard, insensible, etc.). Marble cake is attested from 1864.

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unconscious (adj.)
1712, "unaware, not marked by conscious thought," from un- (1) "not" + conscious. Meaning "temporarily insensible, knocked out" is recorded from 1860. Related: Unconsciously; unconsciousness. In psychology, the noun the unconscious (1876) is a loan-translation of German das Unbewusste. The adjective in this sense is recorded from 1912.
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relentless (adj.)

"incapable of relenting, unmoved by pity, unpitying, insensible to the distress of others," 1590s, from relent + -less. Related: Relentlessly; relentlessness. Relenting is from 1590s as a present-participle adjective, "inclined to relent; too easily moved." For a noun for the group, relentment "act or state of relenting" (1620s) has been tried.

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anesthetic (adj.)
1846, "insensible;" 1847, "producing temporary loss of sensation," with -ic + Latinized form of Greek anaisthetos "insensate, without feeling; senseless, tactless, stupid" (see anesthesia). Noun meaning "agent that produces anesthesia" first used in modern sense 1848 by Scottish doctor James Young Simpson (1811-1870), pioneer in the surgical use of chloroform.
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