Let's look at the first and "original" formula for the dismissal:
Go forth, the Mass is ended. Heb 13:13One thing should be made clear right away: this is not a literal translation of the Latin. A literal translation of Ite, missa est would be something like “Go, it is the dismissal,” but that fails to capture the spirit of the words; it seems rather flat and cold, and does not evoke the same reaction as, say, “Lift up your hearts!” The new translation renders ite as “Go forth” and not just “Go”.
The Latin word missa is where we get the name "Mass" from. Why would we name this liturgy after what is practically the last word said, the last part of the Mass? Pope Benedict XVI explained the significance of this word:
After the blessing, the deacon or the priest dismisses the people with the words: Ite, missa est. These words help us to grasp the relationship between the Mass just celebrated and the mission of Christians in the world. In antiquity, missa simply meant “dismissal.” However in Christian usage it gradually took on a deeper meaning. The word “dismissal” has come to imply a “mission.” These few words succinctly express the missionary nature of the Church. The People of God might be helped to understand more clearly this essential dimension of the Church’s life, taking the dismissal as a starting-point. (Sacramentum Caritatis 51)The word “dismissal” is related to “mission” which comes from the Latin word missa which gives us the word “Mass”! The dismissal is not just a sending-forth, it is a sending-forth on a mission, the mission of the Church, delivered to the Apostles by Jesus before He ascended into Heaven: “Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you.” (Mt 28:19-20)
We will further consider this mission as we look at the other options for dismissal.