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]
The slow-moving mammal first so called 1610s, a translation of Portuguese preguiça "slowness, slothfulness," from Latin pigritia "laziness" (compare Spanish perezosa "slothful," also "the sloth").
disease evidenced by lowness of spirits, sluggishness, indolence, loss of interest in amusements, a wish to be alone, etc., 1765, from hypochondria in its older sense of "melancholy without cause," treated here as a disorder of the body and given the medical ending -osis to denote "a state of disease." The definitions of hypochondria then expanded to include this sense and that has become the usual word for it.
To call the Hypochondriaſis a fanciful malady, is ignorant and cruel. It is a real, and a ſad diſeaſe : an obſtruction of the ſpleen by thickened and diſtempered blood ; extending itſelf often to the liver, and other parts ; and unhappily is in England very frequent : phyſick ſcarce knows one more fertile in ill ; or more difficult of cure. [J. Hill, M.D., "Hypochondriasis," London, 1766]