What is the origin of the idiom "full of beans" and when to use it?

The origin of the idiom "full of beans" is not definitively documented, but it likely stems from the early 20th century American slang. Originally, the phrase was used to describe lively or energetic behavior, possibly referring to the lively movements of beans when they're cooked. Over time, its meaning evolved to include the idea of someone being full of nonsense or talking without substance, suggesting that they are not being truthful.