'ataractic' originates from Greek, specifically the word 'ataraktikos', where 'a-' meant 'not' and 'taraktos' (from the verb 'tarassein') meant 'disturbed' or 'to disturb'.

'ataraktikos' passed into New Latin/medical Latin (as 'ataracticus' or related forms) and later into modern English (19th century) as 'ataractic'.

Initially it meant 'not disturbed' or 'pertaining to being untroubled', but over time it evolved into the current meaning of 'producing calm; having a tranquilizing effect'.