'baptism' originates from Late Latin, specifically the word 'baptismus', which in turn comes from Greek 'baptismos' (from the verb 'baptizein'), where the root 'bapto/bapto-' meant 'to dip, to immerse'.

'baptism' changed from Greek 'baptismos' into Late Latin 'baptismus', passed into Church Latin and Old French forms, and eventually entered Middle English as 'baptisme' before becoming the modern English 'baptism'.

Initially, it referred specifically to the act of immersion or dipping; over time it came to denote the Christian sacrament of initiation and, figuratively, any initiation or severe first test.