What is waiting for the other shoe to drop?

Waiting for the other shoe to drop is an idiom used to describe the feeling of waiting for something bad or negative to happen, especially after a person has already experienced some kind of disappointment or setback. The phrase originated in the early 20th century when apartment buildings were being constructed with thin walls and floors, making it easy for residents to hear their neighbors' footsteps and activity, especially when they removed their shoes. As a person heard their neighbor drop one shoe, they would anticipate the sound of the other shoe dropping, signaling the end of the disturbance. The idiom has since evolved to describe situations where a person feels on edge waiting for something negative to occur. It can be related to anxiety, stress, or even paranoia, as the person believes that the other shoe will drop at any moment.