"lethargy, listlessness," c.1600, from Latin torpor "numbness, sluggishness," from torpere "be numb, be inactive, be dull," from PIE root *ster- (1) "stiff, rigid, firm, strong" (cognates: Old Church Slavonic trupeti, Lithuanian tirpstu "to become rigid;" Greek stereos "solid;" Old English steorfan "to die;" see stereo-).