'baptistery' originates from Late Latin, specifically the word 'baptisterium', where the Greek root 'baptiz-' (from 'baptizein') meant 'to dip or immerse'.

'baptistery' changed from the Late Latin/Greek word 'baptisterium' and passed through Old French forms like 'baptistere' before entering Middle English as 'baptisterie' and eventually becoming the modern English 'baptistery'.

Initially, it meant 'a place for baptizing (a pool or building for immersion)'; over time it has come to mean more broadly 'the part of a church or a separate building containing the baptismal font' and sometimes simply the font itself.