For the game, see Don't Spill the Beans (game).

Don't spill the beans is an English language idiom

Idiom

Idiom is an expression, word, or phrase that has a figurative meaning that is comprehended in regard to a common use of that expression that is separate from the literal meaning or definition of the words of which it is made...

 That means "to inopportunely or accidentally reveal a secret."

There are a number of folk etymology

Etymology

Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...

 hypotheses for its origin, some attributing it to the ancient Greek voting methodology of gathering beans in a jar, or to agricultural origins. However, the phrase first came into use in the early 20th century, in America, which tends to not fit in with these explanations. It is likely that the phrase originated within the American Great Depression

Great Depression

The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...

, among the transient poor under-culture (the hobo

Hobo

A hobo is a term which is often applied to a migratory worker or homeless vagabond, often penniless. The term originated in the Western—probably Northwestern—United States during the last decade of the 19th century. Unlike 'tramps', who work only when they are forced to, and 'bums', who do not...

culture).

Sometimes the phrase may be changed to spilled the beans, which means, unlike the original phrase, "to have given away or told a secret".