Wikipedia
Corn gluten meal
Corn gluten meal (CGM) is a byproduct of corn (maize) processing that has historically been used as an animal feed. It can also be used as an organic herbicide.
The word gluten here is inexact; there is no true gluten in corn, but simply corn proteins. The expression "corn gluten" is colloquial jargon that describes corn proteins that are neither gliadin nor glutenin. Only wheat, barley, and rye contain true gluten, which is formed by the interaction of gliadin and glutenin proteins.