Coming from Old English, the word “whetstone,” originally spelled “hwetstan,” has been around almost as long as bladed weapons. A whetstone is a fine-grained stone used for sharpening blades. The surface works similarly to sandpaper, but instead of smoothing wood, it sharpens the edge of a metal blade. You may have heard the phrase “whet your appetite” — while the word “whet” has largely dropped out of usage, its meaning is related to “whetstone.” The idiom means “to sharpen your desire for food.”