LASSITUDE
inanition, lassitude, lethargy, slackness
(noun) weakness characterized by a lack of vitality or energy
languor, lassitude, listlessness
(noun) a feeling of lack of interest or energy
lethargy, lassitude, sluggishness
(noun) a state of comatose torpor (as found in sleeping sickness)
Source: WordNet® 3.1
Etymology
Noun
lassitude (countable and uncountable, plural lassitudes)
Lethargy or lack of energy; fatigue.
Listlessness or languor.
Source: Wiktionary
Las"si*tude, n. Etym: [L. lassitudo, fr. lassus faint, weary; akin to
E. late: cf. F. lassitude. See Late.]
Definition: A condition of the body, or mind, when its voluntary functions
are performed with difficulty, and only by a strong exertion of the
will; languor; debility; weariness.
The corporeal instruments of action being strained to a high pitch .
. . will soon feel a lassitude. Barrow.
Source: Webster’s Unabridged Dictionary 1913 Edition