S-Letter Sayings  | 
Spilling the beans refers to someone who makes private information known, but why 
is that? Why beans, and why are they being spilled? Well, it's said that this phrase 
may come from ancient Greece. Apparently, a way they voted back then was with 
beans being placed inside of a jar. There were two different colored beans, the white ones meant yes, while black beans meant no. The votes were supposed to be unanimous, so if the jar was accidentally knocked over and the beans spilled out, then the contents would become known. Hence, the phrase 'spill the beans.'

However, this idiom may not have come from ancient Greece, because the earliest it is found in print, with the meaning 'to divulge private or secret information', is from the early 20th century. For example, in the newspaper Smith's Weekly, 1919, there's a part from it that reads:

    "'Now get a move on and no risks,' he declared finally as his henchmen, who had been in the right mood 
      to 'spill the beans,' moved off quietly and walked nonchalantly past the policeman."
S-Letter Expressions.
Phrases and Idioms

The Phrase 'Spill The Beans' - its Meaning and Origins

Making private or secret information known to others.

Example: A married couple bought their son a gift, and they wanted to surprise him with it a week later. However, not wanting to wait any longer, they decided to spill the beans early and told him what they had bought.
Note: Know Your Phrase has the meanings and origins for quite a few expressions. If you have one in particular that you're trying to find, you might want to use our alphabetical list to navigate around and find it. We also have a list of sports and animal related idioms, with a food one coming later. If you are unable to find the saying that you're looking for, well, perhaps come back another time since more will be added soon. That's all for now!
KnowYourPhrase.com - An Alphabetical List of Common Expressions
These beans are spilling out everywhere! Oh well.
* Come on, spill the beans already and tell me what happened yesterday.