'paedobaptism' originates from Greek, specifically the words 'pais' (παῖς) meaning 'child' and 'baptisma' (βαπτισμα) meaning 'a dipping or washing'.

'paedobaptism' was formed in English by combining the Greek-derived prefix 'paedo-' (from 'pais') with the noun 'baptism' (from Latin 'baptismus' < Greek 'baptisma'); an alternative spelling 'pedobaptism' also appears, and the term was established in theological English by the 17th century.

Initially it referred simply to the baptism of children, and over time it has retained that sense as the term for the practice or the doctrine of infant baptism.