Is it farther or further?
c.1200 (mid-12c. as a surname), "saddle horse for ordinary riding (opposed to a war horse), small horse for ladies," from Old French palefroi (11c.) and directly from Medieval Latin palafredus, altered by dissimilation from Late Latin paraveredus "post horse for outlying districts" (6c.), originally "extra horse," from Greek para "beside, secondary" (see para-) + Latin veredus "post horse; light, fast horse used by couriers," from Gaulish *voredos, from Celtic *wo-red- (cf. Welsh gorwydd "horse," Old Irish riadaim "I ride"), from PIE root *reidh- "to ride" (see ride (v.)). The Latin word passed to Old High German as pfarifrid, where in modern German it has become the usual word for "horse" (Pferd).