Catholic Encyclopedia (1913)/Cantate Sunday
A name given to the fourth Sunday after Easter, from the first word of the Introit at Mass on that day -- "Cantate Domino novum canticum", Sing ye to the Lord a new song -- similar to the names Gaudete and Laetare Sundays, assigned to the third Sunday of Advent and the fourth of Lent. These names, which are as old probably as the twelfth century, appear to have been in common use in the Middle Ages and to have been employed to signify the date in secular affairs as well as ecclesiastical. John of Salisbury, Bishop of Chartres (d. 1182), is one of the earliest writers to use the name.
GUERANGER, Liturgical Year (Worcester, s.d.); HAMPSON, Medii aevi Kalendarium, or Dates, Charters and Customs of the Middle Ages (London, 1841), II, 40.
G. CYPRIAN ALSTON