'antiopsonic' originates from modern scientific English, specifically formed from the prefix 'anti-' (from Ancient Greek 'anti-' meaning 'against') and 'opsonic' (derived from 'opsonin', from Ancient Greek 'opson'/'opsōn' meaning 'relish' or 'food'), where 'anti-' meant 'against' and 'opson' meant 'relish/food'.

'antiopsonic' changed from the adjective 'opsonic' (derived from the noun 'opsonin', coined in early 20th-century biomedical English) by prefixing 'anti-' to create a term meaning 'against opsonization'; thus 'opsonin' → 'opsonic' → 'antiopsonic'.

Initially, the Greek root 'opson' referred to 'relish' or 'food'; in immunology 'opsonin' came to mean a factor that 'makes prey ready to be eaten' by phagocytes (i.e., promotes phagocytosis). 'Antiopsonic' developed to mean 'opposite of that' — preventing or inhibiting opsonization.