'antihypnotic' originates from Greek elements via modern English: specifically the prefix 'anti-' (from Greek 'anti') and 'hypnotic' (from Greek 'hypnos' via Greek 'hypnotikos'), where 'anti-' meant 'against' and 'hypnos' meant 'sleep'.

'antihypnotic' was formed in modern English by combining 'anti-' + 'hypnotic'. It appears in medical and pharmacological literature often first as the hyphenated form 'anti-hypnotic' and later as the closed compound 'antihypnotic'.

Initially it literally meant 'against hypnosis' or 'opposed to inducing sleep'; over time it retained this core sense and is now used to describe drugs, agents, or properties that prevent or counteract hypnotic effects.