Confused parroting

We were in Target today and I couldn't find what I was looking for. Noah, once again picking up on my frustration said, "Jeepers-craps!" This would be a combination of "Jeepers-creepers" which Paul always says, and "Crap" which, apparently mommy says a little too much...oops : )I stared at him for a moment and then turned my back and silently laughed hysterically. I think he noticed though because I heard a little giggle come from him. I turned to him and told him nonchalantly that those weren't very polite words and we shouldn't say them. But a few minutes later, when I asked him to help me look for something, I heard him mutter under his breath again "Jeepers-craps"