Hocus pocus is a purported magical phrase in the style of rhyming and alternating incarnations taken from grimoires. The origin of the term is uncertain, and some have come to believe it means utter nonsense.
One origin is attributed to Ochus Bochus, a legendary magician and demon of the Norse. During the reign of King James I of England, the term hocus pocus was accredited to a self-styled magician, according to A Candle in the Dark: or a Treatise Concerning the Nature of Witches and Witchcraft (1656) by Thomas Ady:
I will speak of one man…who called himself «The King’s Majesties most excellent Hocus Pocus,» and so he was called, because that at the playing of every Tricke, he used to say, «Hocus pocus tonus, talontus, vade celeriter jubeo,» a dark composure of words to blind the beholders, to make his trick to pass more currently without discovery.
More likely, hocus pocus is a corruption and mockery of the Latin hoc est enim corpus meum («this is [indeed] my body») spoken by the priest in the Catholic Mass. Many Protestants think hocus pocus concerning the substantiation, changing of the bread and wine into the body and blood of Christ, of the Catholic Mass, too much like magic.
Hocus pocus is said not to be associated with magic or Witchcraft but with trickery, stage-magic, conjuring, and deceit. Some of these latter activities are associated with sorcery, sometimes referred to a low magic performed for self-gain. A.G.H.
Guiley, Rosemary Ellen.The Encyclopedia of Witches and Witchcraft. New York: Facts On File.1989. p. 161