warble (v.)

late 14c., from Old North French werbler "to sing with trills and quavers" (Old French guerbloiier), from Frankish *werbilon (cognate with Old High German wirbil "whirlwind," German Wirbel "whirl, whirlpool, tuning peg, vertebra," Middle Dutch wervelen "to turn, whirl"); see whirl (v.). Related: Warbled; warbling. The noun is recorded from late 14c.