languor (n.)

c. 1400, "loose" (in reference to bowels), from Latin laxus "wide, spacious, roomy," figuratively "loose, free, wide" (also used of indulgent rule and low prices), from PIE *lag-so-, suffixed form of root *sleg- "be slack, be languid."

In English, of rules, discipline, etc., from mid-15c. Related: Laxly; laxness. A transposed Vulgar Latin form yielded Old French lasche, French lâche. The laxists, though they formed no avowed school, were nonetheless condemned by Innocent XI in 1679.

late 15c., "mournful," from Old French langoros "ill, ailing, suffering, languishing" (11c., Modern French langoureux), from langor "sickness, weakness" (see languor). Meaning "suggestive of languor, weariness, or want of energy," often with a suggestion of seductiveness, is from 1821. Related: Languorously; languorousness.