Expression: Spill the beans

Meaning: To divulge a secret, especially to do so inadvertently or maliciously.

Origin:

The derivation of this expression is sometimes said to be a voting system used in ancient Greece. The story goes that white beans indicated positive votes and black beans negative. Votes had to be unanimous, so if the collector 'spilled the beans' before the vote was complete and a black bean was seen, the vote was halted. That's plausible, but doesn't account for the fact that the phrase is first found in the early 20th century. It's probably best if we concentrate our search there and ignore ancient Greece.

'Spill' has been used as a verb with the meaning of 'divulge' or 'let out' since at least the 16th century. Edward Hellowes' Guevara's Familiar epistles, 1574, contains an example of that usage:

"Although it be a shame to spill it, I will not leaue to say that which... his friends haue said vnto me."