Informant – “You know the story of Macbeth. There are a lot of witches in that play. Legend has it that the curses that they say are real. If you say the name of the Scottish Play in a theater needlessly, that theater is cursed. The name summons the witches and curses. To reverse it, you have to run around three times in a circle and spit, or say your favorite curse word. You also get shunned by your cast, which is not fun.”
Informant – “I heard it from my freshman theater teacher. He was crazy. I said Macbeth in class once and he yelled at me ‘YOU NEVER SAY THE SCOTTISH PLAY’S NAME.’ He almost threw a chair at me.”
I can’t think of any practical application for this superstition, so I believe it exists to create a more complex theater subculture. If you know about it then you are more of an theater person than those who don’t.