To spill the beans is to let out a secret. Spill the beans, do not spill the beans, somebody spilled the beans.
It covers both the accidental and the deliberate, which is why it is gentler than betray. One story traces it to ancient Greek voting with coloured beans in a jar, which would spoil the count if knocked over.
1phrasespill the beansTo let out a secret by accident or on purpose.
“Don't spill the beans about the surprise party before Saturday.”
spill the beans is a telling.
First attested in twentieth-century American English; one account traces it to voting with coloured beans in a jar.
First attested in 20th century American English. One possible origin for the phrase is from an Ancient Greek practice of using different-coloured beans for voting, where spilling the jar containing them would unwantedly reveal the results, though this might be folk etymology.
Etymology from Wiktionary, CC BY-SA
Practised in Idioms