Why is the Eucharist Called a "Host"?
Catholics typically refer to the Eucharistic bread of the Mass as a “host.” Technically speaking, both the bread and the wine are rightly referred to as hosts, but it’s become common to refer to just the bread as the host.1
Catholics believe that, at Mass, the consecrated bread is actually the body and blood of Jesus ― it is the Lord, substantially present in our midst.
A common, but not quite correct, assumption is that the word “host” is used for the bread because, when it’s consecrated, it somehow “plays host” to the presence of Jesus. Perhaps the bread hosts Jesus like Martha hosted him in her home (Lk 10:38-42). More crudely imagined, perhaps the bread is something like a host organism and Jesus is a parasite, as if Jesus has begun to live inside the bread.
But this is not quite right. Speaking of the Eucharist as if bread is somehow playing host to Jesus would imply that, in the consecrated Eucharist, there are two things: bread and Jesus. This position is called “consubstantiation,” and is often (wrongly) attributed to Martin Luther.2
The Catholic position is that, after the consecration, the Eucharist is just one thing: Jesus. Indeed, though the Eucharist looks and tastes like bread, the bread has actually ceased to exist. The Eucharist is Jesus ― Jesus alone ― under the appearance of bread.
So why is the Eucharist called a host?
“Host” comes from the Latin word hostia, which is a “sacrificial offering.” Jesus’s death, of course, was a sacrifice ― a Passover offering ― that was linked up with a meal. “This is my body given for you,” Jesus says, upon breaking bread at the Last Supper. “This cup is the new covenant in my blood, which is poured out for you” (Lk 22:19-20). This is sacrificial language.
Catholics believe that what Jesus did at the Last Supper ― this sacrificial meal ― is precisely what Catholics do at each Mass today. “Do this in remembrance of me,” Jesus instructed them (Lk 22:19). This is why many altars contain images of the Last Supper, like the one pictured above.
The Mass is a sacrifice ― the same single sacrifice Jesus offered on the Cross and at the Last Supper 2,000 years ago. As such, we refer to the Eucharist, the broken bread and broken body of Jesus as a hostia, a sacrifice, a “host.”