'antiatom' originates from Modern English formation combining the Greek-derived prefix 'anti-' and the noun 'atom'. The prefix 'anti-' (from Greek) meant 'against' or 'opposite', and 'atom' comes from Greek 'atomos' meaning 'indivisible'.

'anti-' entered English via Latin and New Latin as a productive prefix meaning 'against/opposite', while 'atom' comes from Greek 'atomos' → Latin 'atomus' → Middle English 'atom', and the compound 'antiatom' is a modern scientific coinage formed in the 20th century as antimatter concepts developed.

Initially, the elements 'anti-' and 'atom' separately conveyed 'opposite' and 'indivisible'. Over time the compound came to mean specifically 'an atom made of antiparticles' in the context of antimatter research.