'postcommunion' originates from Latin and Medieval Latin, specifically the prefix 'post' and the noun 'communio', where 'post' meant 'after' and 'communio' meant 'sharing, communion'.

'communio' (Latin) passed into Medieval Latin and Old French as 'communion' and into Middle English as 'communion'; the prefix 'post-' (Latin) was combined with 'communion' in ecclesiastical usage to form the compound 'postcommunion' in English.

Initially it referred generally to something occurring 'after communion (sharing)'; over time it became specialized in Christian liturgical usage to denote the prayer or rite following the Eucharist.