Damn or Dam?

The other day Zachary was playing his DSi, and John heard him say "Damn!".

John: What did you say?

Zack: Never mind.

John: We don't talk like that, OK?

Zack: OK, I'll save it for Nana and Papa's.

So then John proceeds to tell me. And later I'm in Zachary's room, and I bring it up. He said, "I didn't mean it in a bad way. Like a dam for a river." "Uh-huh," I say. He then apologizes, and says, "but I still love you Mom."

Now which dam/damn do you think he said?