'baptiser' originates from Late Latin, specifically the word 'baptizare,' where the root 'bapt-' ultimately comes from Greek 'baptein' meaning 'to dip'.

'baptiser' changed from Late Latin 'baptizare' into Old French 'baptiser', passed into Middle English (e.g. 'baptysen') and eventually became the modern English forms 'baptise' (verb) and 'baptiser' (agent noun).

Initially it meant 'to dip or immerse' (in Greek usage), but over time it evolved into the specific sense 'to perform the Christian rite of baptism' and the agent meaning 'one who baptises'.