'cantatorium' originates from Medieval Latin, specifically the word 'cantatorium', where the root 'cant-' (from Latin 'cantare') meant 'to sing' and the suffix '-orium' meant 'a place or instrument for'.

'cantatorium' developed in Medieval Latin from the Latin verb 'cantare' plus the noun-forming suffix '-orium'; the term was used in church Latin and passed into English scholarship as a technical ecclesiastical term (via Medieval/Church Latin and later antiquarian usage).

Initially it essentially meant 'a place or thing for singing' (by composition of roots), but over time it came to be used specifically for 'a book of chants used by the cantor' in liturgical contexts.