'pre-baptismal' is formed from the prefix 'pre-' (from Latin 'prae' meaning 'before') combined with 'baptismal' (from Late Latin 'baptismus' and Greek 'baptisma', meaning 'immersion' or 'baptism').

'baptisma' (Greek) became Late Latin 'baptismus', which passed into Old and Middle English as 'baptism' and the adjective 'baptismal'; the prefix 'pre-' was later attached to produce 'pre-baptismal' in Modern English.

Originally the elements meant 'before' + 'baptism/immersion'; the compound has consistently meant 'occurring or pertaining to the time before baptism'.