God forbid they should see your pipi

[Coffee Break]

I encountered the expression "God forbid they should see your pipi", but am struggling to understand it. Could you please let me know what it means? Here is the excerpt:

Rachel: “She didn’t take her eyes off you.”

The Protagonist: “Her eyes off me?”

Rachel: “You’re the most exasperating person I know. Olaf, you explain it to him. Sometimes I think you purposely avoid seeing things. As if you’re scared you’d have to get undressed with the people you really care for and God forbid they should see your pipi.”

- André Aciman, Eight White Nights, Eight Night

This is a novel published in the United States of America in 2010. This novel is narrated by the nameless male protagonist. The protagonist meets Clara at a Christmas party in Manhattan. Now, the protagonist is talking with his friends Rachel and Olaf after Clara has left. When Rachel says that Clara didn't take her eyes off the protagonist, the protagonist does not believe her.

In this part, I wonder what the underlined expression means.

I vaguely guess that "pipi" can be a slang of something, but I have no idea what this underlined part means.

 

[5jj]

Pipi is a childish expression for penis. Does that help?

 

[Coffee Break]

@5jj,

Thank you very much for the explanation.
Oh, I didn't know that "pipi" is a childish expression for "penis"! I learned a new thing all thanks to you.

So, by "God forbid they should see your pipi," the speaker is saying "You think it is absurd when you are in a situation where people you really care get to see your penis, because you are scared of getting undressed."

I sincerely appreciate your help.

 

[Tdol]

You are scared to get undressed in front of people you really care for in case they should see your penis.

 

[Tarheel]

Those are a couple of weird people.

 

[Barque]

As if you’re scared you’d have to get undressed with the people you really care for and God forbid they should see your pipi.”

I'd say this wasn't meant to be taken too literally. Rachel possibly means, "You avoid noticing things like this because you're scared you'll become emotionally involved with someone and you're afraid they'll see your vulnerabilities/weaknesses/real self".