The inexhaustible richness of this sacrament is expressed in the different names we give it. Each name evokes certain aspects of it. It is called: Eucharist, because it is an action of thanksgiving to God. The Greek words eucharistein and eulogein recall the Jewish blessings that proclaim - especially during a meal - God's works: creation, redemption, and sanctification.
Source: Catechism of the Catholic Church (Vatican.va)