From Latin, CANTICUM which means a "song." Often interchanged as the title of the Old Testament book, Song of Solomon.

an Old Testament book consisting of a collection of love poems traditionally attributed to Solomon but actually written much later

'A hymn or song from a bibical text'. Sung during the 'office' services (ie: not Eucharist), they form major items of the choral parts of the service. See Magnificat and Nunc Dimittis ( Evensong), and Venite, Te Deum and Jubilate ( Mattins).