Etymology
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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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insensitive (adj.)
c. 1600, "having little or no reaction to what is perceived by one's senses," from in- (1) "not, opposite of" + sensitive. For sense, see insensate. From 1834 as "having little or no mental or moral sensitiveness;" meaning "without consideration for the feelings of others" attested by 1974. Related: Insensitively.
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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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anesthetize (v.)
"bring under the influence of an anesthetic," 1848, from Latinized form of Greek anaisthetos "insensate, without feeling" (see anesthesia) + -ize. Related: Anesthetized; anesthetizing; anesthetization.
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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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deaf (adj.)

Old English deaf "lacking the sense of hearing," also "empty, barren," from Proto-Germanic *daubaz (source also of Old Saxon dof, Old Norse daufr, Old Frisian daf, Dutch doof "deaf," German taub, Gothic daufs "deaf, insensate"), from PIE dheubh-, which was used to form words meaning "confusion, stupefaction, dizziness" (source also of Greek typhlos "blind," typhein "to make smoke;" Old English dumb "unable to speak;" Old High German tumb).

The word was pronounced to rhyme with reef until 18c. Meaning "refusing to listen or hear" is from c. 1200. As a noun, "deaf persons," from c. 1200. Deaf-mute is from 1837, after French sourd-muet. Deaf-mutes were sought after in 18c.-19c. Britain as fortune-tellers. Deaf as an adder (Old English) is from Psalms lviii.5.

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