'paedobaptist' originates from Greek elements, specifically the words 'pais/paidos' and 'baptistēs' (via New Latin/Medieval Latin), where 'pais/paidos' meant 'child' and 'baptistēs' (from 'baptizein') meant 'one who dips/immerses (to baptize)'.

'paedobaptist' was formed in English by combining the prefix 'paedo-' (from Greek 'pais/paidos' through New Latin/Medieval Latin) and 'baptist' (from Greek 'baptistēs' via Late Latin), and entered theological English usage to denote advocates of infant baptism.

Initially the components signified 'child' + 'one who baptizes,' and over time the compound came to mean specifically 'a person who supports or practices infant baptism.'