Random Thought #122

I saw a cleaning truck today that had the catch phrase "Clean as a whistle". I thought about that phrase. How could that possibly have come into being? A whistle has got to be one of the dirtiest things in the world. Any guesses as to the dirtiest place on the human body? You may have some interesting guesses, but the answer is the mouth. That isn't just metaphorical either. It really is the dirtiest place on your body. That being said, how can something that is stuck in someone's mouth and had spit and saliva blown threw it multiple times be thought of as clean? Anyways, if anyone knows where this saying comes from, I'd be interested to know. Please comment and let me know if you find out. It intrigues me.