I'll tell you about the surprise party, but mum's the word!
Don't breathe a word of this to anyone; mum's the word
He promised he wouldn't reveal the secret, stating, "Mum's the word."
We're planning a surprise for her birthday, so mum's the word, okay?
She whispered the news to me, and I assured her, "Mum's the word."
The detective reminded the witness, "This is confidential, mum's the word."
If you tell anyone, it's all over. Remember, mum's the word
The kids know about the new puppy, but mum's the word until Christmas
He clutched the envelope tightly and said, "My lips are sealed, mum's the word."
They agreed to keep their relationship private for now; mum's the word
I have a big surprise for you.
Oh, tell me! Is it a secret?
Yes, mum's the word. You'll have to wait!
Don't tell anyone, mum's the word
We must keep this a secret from everyone
This information must remain confidential