Is it farther or further?
late 12c., from Old French feble (12c., Modern French faible) "weak, feeble," from Latin flebilis "lamentable," literally "that is to be wept over," from flere "weep, cry, shed tears, lament," from PIE *bhle- "to howl" (cf. bleat). The first -l- was dropped in Old French by dissimilation. The noun meaning "feeble person" is recorded from mid-14c.