Etymology
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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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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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desensitize (v.)

1904; see de- "do the opposite of" + sensitize. Originally of photography development; psychological sense "free from a neurosis" is by 1935. Meaning "make or become insensitive" is by 1955. Related: Desensitized; desensitizing; desensitization.

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blind spot (n.)
1864, "spot within one's range of vision but where one cannot see," from blind (adj.) + spot (n.). Of the point on the retina insensitive to light (where the optic nerve enters the eye), from 1872. Figurative sense (of moral, intellectual, etc. sight) by 1907.
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indolence (n.)

c. 1600, "indifference to pain," from French indolence (16c.) or directly from Late Latin indolentia "freedom from pain, insensibility," abstract noun from Latin indolentem (nominative indolens) "insensitive to pain," from in- "not, opposite of, without" (see in- (1)) + dolentem (nominative dolens) "grieving," present participle of dolere "suffer pain, grieve" (see doleful). Originally of prisoners under torture, etc. The intermediate sense "state of rest or ease neither pleasant nor painful" (1650s) is now obsolete as well; main modern sense of "laziness, love of ease" (1710) perhaps reflects the notion of avoiding trouble (compare taking pains "working hard, striving (to do)").

The Castle hight of Indolence,
And its false Luxury;
Where for a little Time, alas!
We liv'd right jollity.
[Thomson, "The Castle of Indolence," 1748]
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