Where did that phrase come from? Spilling the beans

Back during Ancient Greece, they used beans to signify votes. White beans meant "Yes" and black beans "No". The votes had to be unanimous for the motion to go through. However, it the one gathering the votes spilled the jar and a black bean was discovered, voting came to a halt.

The vote collector let the verdict slip before everyone had a chance to vote and all because he "spilled the beans"

And now you know!