'post-baptismal' originates from Latin and Greek elements, specifically the Latin prefix 'post' (from Latin 'post', meaning 'after') and the Greek word 'baptizein' (via Late Greek 'baptisma' and Late Latin 'baptismus'), where 'baptizein' meant 'to dip or immerse'.

'baptismal' entered English via Late Latin 'baptismalis' (from Greek 'baptisma'), and the Latin prefix 'post-' (meaning 'after') was later attached in English to form the compound 'post-baptismal'.

Initially it referred to matters 'pertaining to baptism' (i.e., 'of or relating to baptism'), and with the addition of 'post-' it specifically came to mean 'occurring or relating to the time after baptism'.