The story
Referring to a scene in which the Wizard of Oz hides behind a curtain to project an intimidating shadow image.
Etymology from Wiktionary, CC BY-SA 4.0.
Wizard of Oz experiment
Today it means: In the field of human-computer interaction, a research experiment in which subjects interact with a computer system that they believe to be autonomous, but which is actually being operated by an unseen human being. Full definition →