More about lassitude
The primary meaning of lassitude is “weariness of mind or body, listlessness,” but lassitude has a second meaning, “indolent indifference.” The immediate source of the English word is Middle French lassitude, which, as in English, may be pleasant or unpleasant fatigue. French lassitude comes from Latin lassitūdō, which in Latin always has an unpleasant sense. Lassitūdō is a derivative of the adjective lassus “tired, weary, exhausted,” a derivative of the Proto-Indo-European root lē-, lə– “to let go, go slack,” extended with –d (lēd-, ləd-). The same root yields Greek lēdeîn “to be tired,” Albanian lodhem “to become tired,” and Germanic lētan, which in Old English becomes lǣtan “to allow, permit, suffer” and let in English. Lassitude entered English in the 16th century.