Grunge is the creation of Rachel Benchley and it has been part of every BasicGrey collection since 2008. It became a Moda Basic a few years later.
If you're not familiar with Grunge, it's a unique fabric that is dyed first, then printed on one side to create a unique, textured look. While the printing is the same for all Grunge fabrics, the final look of them can vary widely depending on the number of colors applied, the subtlety or contrast of those colors, and so on.