hypochondriasis (n.)

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]