Post-Communion

After the Canon the priest says the Post-Communion, or prayer after Communion; then he gives the blessing and goes to the other side of the altar, and ends Mass by saying the last Gospel.

Baltimore Catechism No. 4 (of 4) An Explanation of the Baltimore Catechism of Christian Doctrine Thomas L. Kinkead

Originally there was only one collect (and one Secret and Post-Communion) for each Mass.

The Catholic Encyclopedia, Volume 4: Clandestinity-Diocesan Chancery 1840-1916 1913

Gradual and Alleluia or Tract, Gospel, Offertory, Secret, Communion, and Post-Communion, the passages or prayers corresponding to each of these titles being commonly printed in full.

The Catholic Encyclopedia, Volume 10: Mass Music-Newman 1840-1916 1913

The Post-Communion to the Blessing, or now to the end of the last Gospel, forms the last division of the Mass, the thanksgiving and dismissal.

The Catholic Encyclopedia, Volume 3: Brownson-Clairvaux 1840-1916 1913

This is followed by the Post-Communion, a prayer or a Bidding Prayer variable with the day, but with a rather small selection, only a few days having separate proper

The Catholic Encyclopedia, Volume 10: Mass Music-Newman 1840-1916 1913

Just before they started the celebrant said a prayer, the oratio ad collectam (ad collectionem populi); the name would then be the same as oratio super populum, a title that still remains in our Missal, in Lent for instance after the Post-Communion.

The Catholic Encyclopedia, Volume 4: Clandestinity-Diocesan Chancery 1840-1916 1913

At high Mass, as soon as the last Post-Communion is ended, the celebrant and ministers go to the middle of the altar and stand in line.

The Catholic Encyclopedia, Volume 8: Infamy-Lapparent 1840-1916 1913

Post-Communion proper to the feast or day which is being commemorated.

The Catholic Encyclopedia, Volume 4: Clandestinity-Diocesan Chancery 1840-1916 1913

[Post-Communion] is over, that one of the deacons appointed by the archdeacon looks towards the pontiff to receive a sign from him and then says to the people: Ite missa est.

The Catholic Encyclopedia, Volume 8: Infamy-Lapparent 1840-1916 1913

The Secret and Post-Communion are also collects, formed on the same model as the one before the Epistle.

The Catholic Encyclopedia, Volume 4: Clandestinity-Diocesan Chancery 1840-1916 1913