Definition & Meaning of "big mouth"

What is the origin of the idiom "big mouth" and when to use it?

The origin of the phrase "big mouth" is not definitively known, but it likely stems from the idea that a person with a physically larger mouth would be more prone to speaking loudly or indiscreetly. The term has been in use since the early 20th century and has become a common expression in English to describe someone who talks too much or shares information without discretion.