'metazoan' originates from Greek, specifically the word 'metazōon', where 'meta-' meant 'after' or 'beyond' and 'zōon' meant 'animal'.

'metazoan' changed from the Greek word 'metazōon' into New Latin 'Metazoa' and then into the modern English term 'metazoan'.

Initially, it referred to 'animals as distinct from single-celled organisms (protozoa)', but over time it evolved into the current biological sense of 'multicellular animals'.