An Etymological Dictionary of Astronomy and Astrophysics

1. To undergo change in form, substance, appearance, etc.
   
2. To change or alter. → covariance.

Etymology (EN): M.E. varien, from O.Fr. varier, from L. variare “change, alter, make different,” from varius “variegated, different, spotted.”

Etymology (PE): Vartidan “to change,” from Mid.Pers. vartitan “to change, turn” (Mod.Pers. gardidan “to turn, to change”); Av. varət- “to turn, revolve;” cf. Skt. vrt- “to turn, roll,” vartate “it turns round, rolls;” L. vertere “to turn;”
O.H.G. werden “to become;” PIE base *wer- “to turn, bend.”