early 14c., "fail in strength, exhibit signs of approaching death," from languiss-, present participle stem of Old French languir "be listless, pine, grieve, fall ill" (12c.), from Vulgar Latin *languire, from Latin languere "be weak or faint" (from PIE root *sleg- "be slack, be languid"). Weaker sense of "be lovesick, grieve, lament, grow faint," is from mid-14c. Related: Languished; languishing.