'ataraxia' originates from Ancient Greek, specifically the word 'ἀταραξία' (ataraxía), where the prefix 'a-' meant 'not' and 'tarachē' meant 'disturbance'.

'ataraxia' was used in Ancient Greek philosophy (Epicureanism, Pyrrhonism) as 'ἀταραξία'; it passed into Late Latin/Neo-Latin as 'ataraxia' and was borrowed into English via philosophical and classical scholarship in the modern period.

Initially, it meant 'absence of disturbance' or 'imperturbability' as a technical philosophical state; over time it broadened to a general sense of calmness or freedom from anxiety.