'processional' originates from Late Latin, specifically the word 'processionalis', where 'processio' meant 'a going forward' or 'a procession'.

'processionalis' in Late Latin was used in Medieval Latin and Old French forms and eventually passed into English as 'processional' with the same basic form and meaning.

Initially, it meant 'pertaining to a procession', and over time it has retained this primary sense while extending to related musical and liturgical uses.