*weip-

Proto-Indo-European root meaning "to turn, vacillate, tremble ecstatically." 

It forms all or part of: gimlet; gimp (n.2) "ornamental trimming material;" vibrant; vibrate; vibration; vibrato; vibrissa; waif; waive; waiver; whip; wimple; wipe.

It is the hypothetical source of/evidence for its existence is provided by: Latin vibrare "set in tremulous motion, move quickly to and fro, quiver, tremble, shake," Lithuanian vyburti "to wag" (the tail), Danish vippe, Dutch wippen "to swing," Old English wipan "to wipe."