It's a burp, right?

Zach doesn't like to lie still...ever, but especially not for diaper changes.  So, I usually give him a toy, or tickle him enough to let him know that I'll go as fast as he lets me.  Well, during one of the tickling episodes today, he farted.  I said to him, "You farted!" with a big smile on my face, because it was funny.  He looked so confused, so I then said, "You had a butt burp; your butt burped."  He thought about this for a very little bit, and then said to me, "butt burp."