What originally had been a somewhat mysterious belief that Christ was actually present during communion had morphed into an increasing belief that he was actually present in the communion elements themselves. This led the parishoners to increasingly decline the elements altogether out of a belief they were not worthy to handle the physical body and blood of Christ. What if they spilled it? Abstention from the Eucharist got so bad, the church had to mandate at least annual participation.
When the west rediscovered the philosophy of Aristotle and his belief in the separation of the accidents of an item (the look and feel) and its substance (the essence of it), the pieces were in place for the doctrine of transubstantiation, that the bread and wine miraculously became the actual, physical body and blood of Christ. The Fourth Council of the Latemer formalized this belief in 1215.
This led to other changes, foremost of which was the church stopped offering the communion cup altogether – if Christ’s physical body is in the bread, then so must be his blood, so the wine was unnecessary. Further, what can only be described as the idolization of the bread increased.
After preparing the elements, the priest would quietly give the prayer of invocation. The Mass, being Latin, would have been unintelligible to the congregants, and this prayer was no different. The church had long before determined that during the prayer, Christ’s body entered the “host” (from the Latin hostia, meaning “victim”) exactly as the priest recited Christ’s Passover words, “This is my body.” As the moment approached, the congregation would yell, “Heave it high!” In response, the priest would raise the plate with the bread high above his head, and he would call out the magic words: Hoc est corpus meum! A bell would ring, and the host would be transformed. Jesus would be sacrificed again for their sins.
The priest would then carry the host down the aisle so that congregants could gaze upon it; those looking at it, regardless of motive or relationship with God, would gain divine merit through God’s grace, the church taught, ex opere operato – “from the work performed,” not from anything done by the worshippers. Sometimes he would carry it through the streets of the city so villagers could bring their sick in hopes of being healed by looking at the body of Christ. Before going to battle, generals could have a priest perform a communion-only Mass in their tent, so that by gazing at the host, he might have success in battle.
These developments – withholding the cup from the laity, the doctrine and consequences of transubstantiation and the doctrine of Mass as a good work of sacrifice – were the driving forces of the German priest Martin Luther’s 16th century reformation efforts (he called Aristotle “the devil’s whore,” among other hyperbolic statements about the church’s doctrinal underpinnings). While the Catholic Church still practices transubstantiation, the rest of it, as far as I’m aware, has largely been jettisoned.
But there is one vestige of the medieval Mass that we have with us.
When the priest would take the host and “heave it high,” uttering the magical, mysterious words Hoc est corpus meum, the congregation had no idea what he was saying. They could only take what they heard and transliterate it for themselves. So they did.
And that is why, when magicians are about to perform their own acts of magic, they utter the words Hocus pocus.