Code word for Danger as explained in the series "Friends"
Joey: Well, you wouldn't let me in, so I thought you were in trouble.
Chandler: Well, we're not.
Joey: But you called me 'Bert'!? That's our code word for danger!
Chandler: We don't have a code word.
Joey: We don't? We really should. From now on, 'Bert' will be our code word for danger.