Yucky Gerps!

I was using some antibateria spray, while driving in the car. Peter asked what that 'thing was, the thing that you shake and spray'? I told him that it was a soap spray that gets rid of germs.
He asked, "What are GERMS?"
I said, "Germs are yucky things that sometimes stick to your skin, and sometimes they can even make you sick, so this soap helps to get rid of them!"
Peter replied, "Oh. . . . just like BIRDS!!!!"
I knew that he must have had a good point, somehow, so I asked what he meant.
Peter said "You know. . . . like the birds. . . .they say 'gerp gerp'!
I laughed, "Peter, birds say 'cherp', I said 'GERMMMMSSS'"
He laughed back.