neither: [13] Despite the two words’ similarity, neither is not just either with a negative prefix tacked on. It comes ultimately from Old English nāhwæther ‘neither’, a compound formed from nā ‘not’ (which survives as no in modern English ‘whether or no’) and hwæther ‘which of two’ (ancestor of modern English whether). In the late Old English period it was contracted to nawther, and in Middle English, under the influence of either, this became transformed into neither. => whether
