'baptistry' originates from Late Latin, specifically the word 'baptisterium', where 'baptister-' referred to bathing or immersion for baptism.

'baptistry' changed from the Greek word 'baptistērion' into Late Latin 'baptisterium' (and through Medieval Latin/Old French forms) and eventually became the modern English word 'baptistry'.

Initially, it meant 'a place for bathing or immersion,' but over time it evolved into its current meaning of 'a place or building in Christian churches used for the sacrament of baptism' (and by extension, the baptismal font itself).