Hocus Pocus or hocus-pocus is a generic term that may be derived from an ancient language and is currently used by magicians, usually the magic words spoken when bringing about some sort of change. It was once a common term for a magician, juggler, or other similar entertainer.
The origins of the term remain obscure. According to the Oxford English Dictionary the term originates from hax pax max Deus adimax, a pseudo-Latin phrase used as a magic formula by conjurors. Some believe it originates from a corruption or parody of the Roman Catholic liturgy of the Eucharist, which contains the phrase "Hoc est enim corpus meum". This explanation goes back to speculations by the Anglican prelate John Tillotson, who wrote in 1694:
"In all probability those common juggling words of hocus pocus are nothing else but a corruption of hoc est corpus, by way of [...] imitation of the priests of the Church of Rome in their [...] Transubstantiation."
Others believe that it is an appeal to the Norse folklore magician Ochus Bochus:
"Hocus Pocus: Words of pseudomagical import. According to Sharon Turner in The History of the Anglo-Saxons (4 vols., 1799-1805), they were believed to be derived from "Ochus Bochus," a magician and demon of the north."
"Some have suggested the phrase predated His Majesties Hocus Pocus, being corrupted from the name of a demonic sorcerer of Norse folklore, Ochus Bochus. Ochus Bochus is himself quite possibly a corruption of Bacchus, god of conjuration who turned water into sacred wine. Bacchus/Bochus could well be related to Jesus who turned water into wine, wine into his own blood, & bread into his flesh (all coopted from Dionysianism)."
The Welsh hovea pwca (a "goblin's trick" or hoax) could also be the source:
"One further speculation is that Hocus Pocus is derived from the Welsh term Hovea Pwca, a hoax perpetrated by a hob-goblin or will o' the wisp called a Pwca, Pooka, or having the personal name Puck. This creature was a shape-shifter whose name recurs throughout Europe as a name of the devil, inclusive of Ochus Bachus."
Or it may simply be imitation Latin with no meaning, made up to impress people:
"I will speak of one man... that went about in King James his time... who called himself, The Kings Majesties most excellent Hocus Pocus, and so was he called, because that at the playing of every Trick, he used to say, Hocus pocus, tontus talontus, vade celeriter jubeo, a dark composure of words, to blinde the eyes of the beholders, to make his Trick pass the more currently without discovery, because when the eye and the ear of the beholder are both earnestly busied, the Trick is not so easily discovered, nor the Imposture discerned." — Thomas Ady, A Candle in the Dark, 1656