mum's the word
Meaning
To keep a secret and not reveal any information.
Origin
Imagine the very first sound of silence—that closed-mouth, lips-pressed gesture we still instinctively make for 'be quiet.' From this primal utterance, the word 'mum' emerged in English as far back as the 14th century, a simple yet powerful command for silence, perhaps mimicking the sound of a closed mouth. Even Shakespeare used 'mum' to denote secrecy and quiet. But it wasn't until the 18th century that this ancient call for quietness evolved into the common phrase 'mum's the word,' cementing its place in our language as the ultimate, punchy instruction to keep a secret under tight wraps.
Examples
- I know who won the raffle, but mum's the word until they announce it officially.
- Remember, we're planning a surprise party for Sarah, so mum's the word when you see her.