This idiom means to refrain from speaking or to hold back from saying something, especially to avoid offense, argument, or revealing a secret. It suggests self-restraint in conversation, often used as a command or advice to stay silent in delicate situations.

The phrase likely originates from the physical act of biting one’s tongue to prevent speech, a gesture associated with restraint since medieval times. An early use appears in Shakespeare’s *Henry VI, Part 2* (1591): ‘Bite thy tongue.’ By the 17th century, it was a common proverb, as seen in John Ray’s 1678 *English Proverbs*. Its use grew in the 19th century, particularly in British literature, to describe social tact or secrecy, reflecting norms of polite restraint.