Obviously, some of you already know that this fairly informal phrase means, essentially, ”to disclose a secret”.
A more complete definition is that the secret is usually revealed by accident or imprudently, and that "spilling the beans" often ruins some surprise or other plan.
"Spill" is the core term here, with "beans" a kind of filler; much as it is in the similar phrase spill it.
"Spill" came into Old English as spillan, "to kill". Middle English spillen continued this theme of slaughter and destruction: "to kill, destroy, shed (blood)".
The theme survives today in the retained phrase "spill blood", meaning "to kill or wound". The term gradually ameliorated as, between the 10th and the 18th centuries, it came to mean "to ruin something, ruin the soul of someone, injure morally, or waste something, like time or effort".
The present sense of causing something to fall from or pour out of a container still connotes wasting or ruining the contents.I have also found a 1574 quote for spill it meaning "to divulge, to let out". The spilling of beans endures. Over the years, there have been countless variations of form and meaning, all with "spill". You can "spill the works / the soup / everything / what you know and your guts". Or you can just plain spill.
So now everything is clear for "TO SPILL" but we still don't know anything about "BEANS".
And now here we are with a WEBSITE that has been alive and kicking for almost 15 years now.
I SPILLED THE BEANS !