The Scottish Play
It's a common superstition among actors, directors, and stagehands to avoid saying aloud the name Macbeth while in the theatre itself, under the belief that to do so will bring bad luck and/or curse the production. To avoid it, most theatre people refer to the Shakespearean tragedy as "The Scottish Play."
According to folklore, Macbeth was cursed from the beginning. It was widely believed that a coven of witches objected to Shakespeare using real incantations in the script, so they put a curse on the play.