The emerald cut has a long and distinguished history: it’s based on the earliest faceted diamond shape called the table cut. In the 14th century, cutters discovered that they could use diamond dust to grind away the top point of a diamond crystal creating a flat table facet that allows you to see into the stone. Later they added a faceted culet on the bottom.
These early step cuts were refined over the centuries, becoming popular in Art Deco jewelry designs in the 1920s. Step cuts were particularly popular for emeralds because the beveled corners of the shape protect the corners against chipping while still providing bright flashes of color. The rectangular step cut, which suits the natural elongated shape of emerald crystals, became so closely associated with these green gems that it was named after them.