'antimanic' originates from Modern English, specifically formed from the prefix 'anti-' (from Greek 'anti' meaning 'against') and 'manic' (from Greek 'manikos', from 'mania', meaning 'madness' or 'frenzy').

'manic' ultimately comes from Greek 'mania' (μανία), passed into Late Latin and then into English as 'mania'; the prefix 'anti-' (ἀντί) was combined with 'manic' in Modern English to form the compound 'antimanic' (also seen as 'anti-manic').

Initially the components meant 'against' + 'madness'; over time the compound has come to mean specifically 'against mania' in a medical/therapeutic sense, i.e., relating to prevention or treatment of manic symptoms.