big mouth, have a

big mouth, have a

Also, have or be a loud mouth . Be loquacious, often noisily or boastfully; be tactless or reveal secrets. For example, After a few drinks, Dick turns into a loud mouth about his accomplishments, or Don't tell Peggy anything confidential; she's known for having a big mouth. [Slang; late 1800s]
See also: big, have