Languor
Etymology
From Latin “languor” (faintness, weariness), from “languere,” to be faint or listless, reaching English through Old French “langour.” The word can lean either way — toward the agreeable drowsiness of leisure or toward a sapping, dispiriting lassitude — depending on whether the stillness is welcome.
noun · /LANG-gur/
A pleasant or oppressive heaviness of body and mind marked by inactivity and lack of energy.
What it names
The dreamy, slowed-down weariness of a hot afternoon, when moving feels needless and stillness feels sweet.
Example
The whole village dissolved into languor after lunch, shutters half-closed against the July heat.
Related idea
Plain fatigue is depletion that rest will cure; languor is a mood of soft heaviness, often enjoyed, in which one has no wish to be roused at all.