Origins
The word 'neither' descends from Old English 'nāhwæþer' (also contracted as 'nawþer' or 'nāþer'), meaning 'not either' or 'not which of the two.' It is a compound of 'nā' (no, not) and 'hwæþer' (which of two, whether), from Proto-Germanic *nē (not) + *hwatharaz (which of two), from PIE *ne (not) + *kʷoteros (which of two), from the interrogative stem *kʷo- (who, which, what).
The word belongs to a triad that reveals the internal logic of Old English pronoun formation. 'Whether' (Old English 'hwæþer') asks the question: which of two? 'Either' (Old English 'ǣghwæþer,' literally 'each of two') provides the inclusive answer: each one. 'Neither' (Old English 'nāhwæþer,' literally 'not which of two') provides the exclusive answer: not one. All three share the '-ther' element from Proto-Germanic *hwatharaz, the dual interrogative pronoun — a word that specifically asked about a choice between two options, not three or more.
The PIE interrogative stem *kʷo- is one of the most important roots in the language family, generating all of the English 'wh-' question words (the 'hw-' in Old English, before the consonant cluster reversed to 'wh-'): 'who' (*kʷos), 'what' (*kʷod), 'which,' 'where' (*kʷor), 'when' (*kʷom), 'why,' and 'how' (from a related form). In Latin, the same stem became 'qu-': 'quis' (who), 'quid' (what), 'quod' (which), 'quandō' (when), 'quāre' (why). The sound correspondence PIE *kʷ → Germanic 'hw' → Latin 'qu' is one of the most regular in comparative linguistics.
Spelling and Pronunciation
The pronunciation of 'neither' varies dialectally. British English traditionally favors /ˈnaɪðər/ (rhyming with 'bother' in non-rhotic accents), while American English often uses /ˈniːðər/ (with the long 'ee'). Both pronunciations have been documented since at least the eighteenth century, and Ira Gershwin immortalized the variation in the song 'Let's Call the Whole Thing Off' (1937): 'You say either and I say either, You say neither and I say neither.'
The grammar of 'neither...nor' has generated extensive discussion among grammarians. The construction 'neither X nor Y' negates both members of a pair: 'neither rain nor snow,' 'neither here nor there,' 'neither fish nor fowl.' The question of verb agreement — 'neither he nor she was/were there' — remains debated, with authorities variously recommending agreement with the nearest noun, agreement with the plural (since two subjects are involved), or avoidance of the construction altogether.
In logic, 'neither' performs a specific function: it expresses the negation of a disjunction. 'Neither A nor B' is equivalent to 'not A and not B' (by De Morgan's laws). The logical operator NOR (neither...nor) is one of the functionally complete operators in Boolean logic — every possible logical function can be constructed from NOR gates alone, making it a fundamental building block of digital circuits.
Old English Period
The word's erosion from Old English 'nāhwæþer' to modern 'neither' — losing two full syllables — illustrates the general principle that high-frequency function words undergo more phonological reduction than content words. Grammar words are spoken quickly and unstressed, and over centuries they wear down to their minimal recognizable form.