The name originally came from demin fabric that was washed in large commercial vats, with small pumice pebbles to give a worn, faded look.

Now it just means a color of jeans called stonewash, or in other words, worn faded jeans.  If you want your ‘plain’ jeans to look stonewashed, soak them in cold water for several hours, then rub sandpaper over them until they gain the proper worn look, and wash as usual.

You can buy a package of dye at the store called “stonewash”.