It originated from a voting practice in ancient Greece. Beans were used as ballots, and if someone accidentally dropped their beans (spilled the beans), they would reveal their vote.
Today, it's used figuratively to describe any situation where someone accidentally or intentionally reveals confidential information.
Here are some examples:
* "I'm so sorry, I didn't mean to spill the beans about your surprise party."
* "She's going to spill the beans about everything if you don't stop her."
* "He spilled the beans about the company's new product launch."