swear words and a three year old

Oh my goodness.
Jaxton was in his room playing last night while I was doing dishes and I heard him talking to himself (or maybe his toys, who knows).  I couldn't make out what he was saying but I did think to myself that it was cute he was keeping himself happily amused.  Just then, he comes running into the kitchen to tattle on himself.  I love that he's so little that he tattles on himself.  It makes me laugh.  So I'm standing there washing dishes and he says to me, "Mommy, I say oh shit and dammit!" and then he covered his mouth because he knows these are not nice words.  So I say to him "Buddy, where did you hear those words?"  I kind of  cringed a little inside and half expected him to say me or Mitch but instead he says, "in a song on the radio in the car".  This confused me since we are pretty careful about what he sees and hears.  Putting aside my confusion, I calmly explained that even though we hear these words sometimes, it is not nice to say them and we shouldn't repeat it.  He says to me, "yah ok." and then continues to say "what I say, Mommy?".  I said "Buddy I'm not gonna repeat what you said.  Those are not nice words.".  He said again, "No Mommy, what I say?"  Then it dawned on me that he wanted to know what he should say instead, as if all he ever hears are swear words and he doesn't know of any other options.  So I told him, "Well, you could say, 'oh darn', or 'aw schucks', or 'oh gosh'."  He thought about this for a minute and then gave a nod of approval. He then continued to pace the kitchen for quite a long time, practicing these more appropriate words, as if they were completely new to him.  It killed me and I couldn't help but laugh.