'antidemoniac' originates from Greek and Late Latin elements: the Greek prefix 'anti-' (from Greek 'antí') meaning 'against' and the Late Latin/Greek term 'daemonium'/'daimonion' meaning 'spirit' or 'lesser divine being'.

'antidemoniac' developed as a coinage combining 'anti-' + 'demoniac' (from Medieval/early modern English 'demoniac', itself from Latin 'daemonium' via Greek 'daimonion') to mean something against demons; the modern English form preserves these elements.

Initially formed to express simple opposition to spirits ('against spirits'), the term's use narrowed to describe practices, qualities, or persons that counteract demonic possession or influence.