A thousand years ago, you did not say your kitchen knives needed to be sharpened: you said they needed to be whetted. In fact, the word sharpen was not used to describe the act of giving a knife a better cutting edge until the sixteenth century. Once established, however, the word sharpen gradually overtook whet, so that nowadays whet is commonly used in only two places: in whetstone, the name of a fine-grained stone used to sharpen blades, and in whet your appetite, a phrase used since at least the sixteenth century to mean to sharpen or stimulate your desire for food. The familiarity of the expression whet your appetite has also beguiled many writers into wrongly using the word whet in the expression whet your whistle, meaning to take a drink. The original and more sensible form of this expression is wet your whistle, an idiom dating back to the fourteenth century (even Chaucer used it in The Canterbury Tales). The mistaken substitution of whet your whistle for wet your whistle was common throughout the seventeenth and eighteenth century but is less frequent now for the simple reason that whet has become a far less familiar word.