late 12c., "lacking strength or vigor" (physical, moral, or intellectual), from Old French feble "weak, feeble" (12c., Modern French faible), dissimilated from Latin flebilis "lamentable," literally "that is to be wept over," from flere "weep, cry, shed tears, lament," from PIE *bhle- "to howl" (see bleat, v.). The first -l- was lost in Old French. The noun meaning "feeble person" is recorded from mid-14c.