Is it farther or further?
c.1300, from Old North French werbler "to sing with trills and quavers," from Frankish *werbilon (cf. Old High German wirbil "whirlwind," German Wirbel "whirl, whirlpool, tuning peg, vertebra," Middle Dutch wervelen "to turn, whirl"); see whirl. The noun meaning "tune, melody" is recorded from c.1300. Related: Warbled; warbling.