Old English hwider, from Proto-Germanic *hwithre-, from *hwi- "who" (from PIE root *kwo-, stem of relative and interrogative pronouns) + ending as in hither and thither. Compare Gothic hvadre.
whiteness
white-out
white-tail
whitewash
whitey
whither
whithersoever
whitish
whitlow
Whitsun
Whitsunday