In the Catholic Liturgy, the word host signifies the circular particle of unleavened bread consecrated in the Mass together with the wine.
In the broad sense, the Latin word hostia means victim; thus, in the Roman Empire, hostia could mean the soldier killed in combat, in defence of his country. In the stricter sense, however, hostia meant victim, human or animal, offered to the gods to placate their wrath. Therefore, its more proper meaning was that of an expiatory victim.
Now, the expiatory victim par excellence is Our Lord Jesus Christ, the Lamb of God, immolated on the Cross for the redemption of all humanity. Thus, as the Mass is the unbloody renewal of the Sacrifice of Calvary, it is most fitting that the name “hosts” be given to the particles of bread which, in the act of Consecration, are transubstantiated into the Body of Jesus Christ, our Redeemer. ″