My late mother gave me this book for xmas years ago, and I'm only just now reading it cover-to-cover. It's wonderfully funny and fascinating, and I could post something from it on this thread every day but I won't.
So I'll just give you this: the term Hocus Pocus
comes to us from the jester of the court of King James I (he of King James Version Bible fame). James was a Protestant who enjoyed jokes at the expense of Catholics, and his court jester was what we would now call a Comedy Magician. Whenever he would change something into something else he'd say "Hocus Pocus!" - a comedic perversion of the Latin words a Catholic priest would say when "magically" transubstantiating a piece of bread into a piece of Christ's body during communion, Hoc est corpus meum
("This is my body"). It caught on, obviously.
"Hocus pocus" eventually begat the word "hoax," which in turn begat "hokum."