Origins
The word 'man' is one of the most semantically transformed in the English language, having undergone a dramatic narrowing from universal to gendered over roughly a thousand years. In Old English, 'mann' was entirely gender-neutral, meaning 'human being' or 'person' regardless of sex. To specify an adult male, Old English used 'wer' (cognate with Latin 'vir,' as in 'virile') or 'wǣpnedmann' (literally 'weapon-person,' a reference to male genitalia as 'weapons' — a surprisingly crude coinage from the Anglo-Saxons). To specify a female, Old English used 'wīf' (woman, wife) or 'wīfmann' (female person), which eventually contracted into 'woman.'
The Proto-Germanic ancestor *mann- meant 'human being' and was also gender-neutral. Its further origin is debated. The traditional derivation connects it to PIE *man- (man), attested in Sanskrit 'Manu' (the first human being in Hindu mythology, cognate with the Norse 'Mannus,' the legendary ancestor of the Germanic peoples, recorded by Tacitus). An alternative and increasingly popular theory derives it from PIE *men- (to think), making 'man' literally 'the thinking one' or 'the one endowed with mind.' If this second derivation is correct, then 'man,' 'mind,' 'mental,' and 'memory' all share the same root.
The narrowing from 'person' to 'adult male' was gradual. In early Middle English (12th–13th centuries), 'man' could still mean any person — it was used in contexts where we would now say 'one' or 'someone.' But the older sex-specific term 'wer' was already falling out of use (surviving only in 'werewolf'), leaving a gap. 'Man' gradually filled both roles: generic 'person' and specific 'adult male.' By the late medieval period, the male-specific meaning had become dominant, and the generic sense was becoming archaic, though it lingered in compounds like 'mankind' and legal phrases like 'manslaughter' (person-slaying, not male-slaying).
Greek Origins
The Germanic cognates show the same original neutrality. German 'Mann' has also narrowed to mean 'adult male,' though the indefinite pronoun 'man' (one, people in general) preserves the older gender-neutral sense. Dutch 'man' and the Scandinavian cognates followed similar paths. Gothic 'manna,' preserved in Wulfila's fourth-century Bible translation, meant 'person' and was used to translate Greek 'ánthropos' (human being), not just 'anér' (adult male).
The cultural consequences of this semantic shift have been debated since at least the eighteenth century. When 'man' meant 'person,' phrases like 'all men are created equal' were linguistically inclusive regardless of how they were applied in practice. As the word narrowed, such phrases became ambiguous — are they using the older generic sense or the newer male-specific sense? This ambiguity has fueled centuries of legal and philosophical argument.
The phonology of 'man' is straightforward: Old English 'mann' had a short 'a' vowel and a geminate (doubled) nasal consonant. The geminate simplified in Middle English, and the short 'a' was raised to /æ/ in most dialects of Modern English. The plural 'men' (from Old English 'menn') shows i-mutation — an ancient vowel change where a back vowel was fronted by an 'i' in the following syllable, the same process that gives us 'foot/feet,' 'goose/geese,' and 'mouse/mice.'