I. conjunction
Etymology: Middle English, alteration (influenced by either) of nauther, nother, from Old English nāhwæther, nōther, from nā, nō not + hwæther which of two, whether
Date: 12th century
not either , also not ,
Usage: Although use with or is neither archaic nor wrong, neither is usually followed by nor. A few commentators think that neither must be limited in reference to two, but reference to more than two has been quite common since the 17th century
II. pro noun
Date: 13th century
not the one or the other of two or more,
Usage: Some commentators insist that neither must be used with a singular verb . It generally is, but especially when a prepositional phrase intervenes between it and the verb , a plural verb is quite common
III. adjective
Date: 14th century
not either ,
IV. adverb
Date: 1551
either , similarly not ; also not