'antivaccinator' originates from English, specifically formed from the prefix 'anti-' (from Greek 'antí') meaning 'against' and the noun 'vaccinator' (from 'vaccinate' + '-or'), where the root 'vaccin-' traces back to Latin 'vacca' meaning 'cow' (via 'vaccinus'/'vaccinare').

'vaccinate' comes from Latin 'vaccinus' ('of or from cows') derived from 'vacca' ('cow'); it entered English in reference to using cowpox to protect against smallpox (vaccination). 'Vaccinator' developed as the agent noun from 'vaccinate', and 'antivaccinator' was formed in modern English by prefixing 'anti-' to indicate opposition.

Initially 'vaccin-' words referred to 'of or from cows' (because of cowpox use); over time 'vaccinate' came to mean 'to inoculate against disease', and 'antivaccinator' now means 'a person opposed to vaccination.'