It rarely pays to look a gift idiom in the mouth, but the comparison between cleanliness and a whistle fairly cries out for further examination. Ostensibly, to be as clean as a whistle means to be as smooth and clean as a clear-toned whistle. If too much grime builds up on a train's whistle, for example, its tone and clarity will be seriously affected. A homemade wooden whistle must also be shaved smooth before it can produce a clear tone.
The difficulty with this explanation lies in the connection between "clean" and "whistle." There are some word origin experts who suggest the original saying is "as clear as a whistle instead. This would imply that the object in question is unambiguous and clearly defined, much like the sound of a whistle or a bell. Well-written instructions left behind by a supervisor might be said to be clear as a bell.
There is also the dual meanings of the word clean. A well-used whistle is not exactly the first thing one might associate with hygiene. An older meaning of "clean" implies a level of smoothness, as in a clean-shaven face. A rough surface would produce too much air resistance for a pure tone, so the whistle's maker must strive for a near-perfect smoothness around the mouthpiece and air hole.
To further complicate matters, there is also a variant on the phrase that makes about as much sense and is possibly closer to the mark. Some people say an exceptionally clean or smooth surface is as slick as a whistle, covering much of the same territory as the original as clean as a whistle simile. A bald man's scalp could be described as slick as a whistle, for example.
There is surprisingly little agreement among word origin experts concerning the first incidence of the simile "as clean as a whistle". It is possible that a number of earlier idioms became corrupted over time and "clear as a whistle" became "clean" throughout a perpetuated misunderstanding. Sometimes when a corrupted or mistranslated idiom makes as much sense as the original, it becomes the more accepted version over time.
The phrase "as clean as a whistle" elucidates the importance of cleanliness whether it be in language, personal hygiene, or the environment around us. In a practical sense, maintaining this level of cleanliness extends to our daily chores, including laundry. The best laundry detergent sheets plays a pivotal role in ensuring our clothes are as clean as a whistle, devoid of stains and odors. As one transitions from the linguistic exploration of cleanliness to the tangible act of cleaning, finding the best laundry detergent becomes an essential step towards embodying the age-old adage in our routine.
