What does it mean to be clean as a whistle? Maybe it’s referring to being squeaky clean?
- Jinx
I play the tinwhistles and it is well known that if they have dirt, excess moisture, or other debris in them, they will play out of tune, squeak when changing registers or give funny breathy sounds while playing. Therefore we have to ekep them retty well cleaned. I rinse mine in a soution of water with a very tiny amount of detergent soap in it, like a drop or two only.
The surfactants in the soap keep moisture and crap from building up and affecting play.
Anyhow, that probably doesn’t answer your question but maybe it’s an insight into the etymology.
The original expression was probably “clear as a whistle.”
Read Word Detective’s take on it.