Zip Your Lip

Max criticizes a sweater's color, leading to a discussion about the idiom 'zip your lip', which means to be quiet or keep something to oneself. The phrase originated in the 1940s with the popularity of zippers. The conversation continues with Max asking if he can speak again, and humorously worrying about lunchtime.

What is the context in which Max is told to 'zip his lip'?

Why might someone be advised to 'zip their lip' in a conversation?

What does the phrase 'zip your lip' mean?

How has the meaning of 'zip your lip' evolved since the 1940s?

What was the earlier phrase used before 'zip your lip' became popular?