'rebaptizer' originates from the prefix 're-' (Latin) meaning 'again' combined with 'baptize,' which ultimately comes from Greek 'baptizein' (βαπτίζειν) meaning 'to dip or immerse.'

'baptize' came into English via Late Latin 'baptizare' and Old French 'baptiser'; the verb 'rebaptize' was formed in English by adding the prefix 're-' to 'baptize,' and the agent noun 'rebaptizer' was later formed with the suffix '-er'.

Initially, the root meant 'to dip or immerse'; over time 'baptize' came to mean 'to admit into the Christian Church by ritual immersion or sprinkling,' and 'rebaptize' acquired the specific meaning 'to baptize again,' which is retained in 'rebaptizer' ('one who baptizes again').