I thought that Cecil had explained the origin of “hocus Pocus” some time back but I can’t find it in the archives. My dictionary says that it is a mangling of 'hoc est corpus meum." But I could have sworn that Cecil said the origin was a 17th century magician.
Yikes, I am totally pulling this one from some dilapidated brain cells somewhere, so don’t make any bar bets on it, okay?
“Hoc est corpus” means “This is the body” in Latin. In Roman Catholic ritual, these are the words that a priest uses at the time of consecration of the bread, wherein transubstantiation is said to occur (the bread becomes the Body of Christ). Although nowadays the Mass is said in the language of the people, up until the early 60s it was said in Latin (making it easier to go to church when you traveled in foreign lands).
“Hocus pocus” is a corrupted form of “hoc est corpus.” Presumably the phrase became “magic words” because of the “holy magic” of transubstantiation.
More of the Straight Dope has quiz questions, which I don’t believe are online.
Question #41 is:
The phrase “hocus-pocus” harks back to some medieval conjurer’s parody of the act of:
a. transfiguration
b. transubstantiation
c. transmigration
d. transvestitism
The answer per Cecil is B, for the reasons as explained by Melin, although Cecil gives the full Latin phrase as hoc est enim corpus meun (“for this is my body”).