'adiaphoron' originates from Greek, specifically the word 'ἀδιάφορον' (adiaphoron), where 'a-' meant 'not' and 'diaphoros' meant 'different.'

'adiaphoron' was borrowed directly from Greek into Latin as 'adiaphoron,' and eventually became the modern English word 'adiaphoron.'

Initially, it meant 'indifferent or neutral matter,' and this meaning has largely remained the same in modern usage.