The word “viaticum” comes from the Latin viaticus, i.e. “of or pertaining to a road or journey.”
Subsequently, “viaticum” figuratively meant the provision for the journey of life, and finally by metaphor the provision for the passage out of this world into the next. It is in this last meaning that the word is used in sacred liturgy.
Therefore, viaticum is the name of Holy Communion when it is given in a public or private manner to someone in danger of death, during an illness, or to soldiers going into battle. It may thus be given without the communion fast and may be repeated during an illness as often as required.
In the presence of the priest, viaticum may also be combined with the sacraments of Confession and the Anointing of the Sick.
The Catechism of the Catholic Church states, “Thus, just as the sacraments of Baptism, Confirmation, and the Eucharist form a unity called ‘the sacraments of Christian initiation,’ so too it can be said that Penance, the Anointing of the Sick and the Eucharist as viaticum constitute at the end of Christian life, ‘the sacraments that prepare for our heavenly homeland’ or the sacraments that complete our earthly pilgrimage (1525). (7:45)