A glut is too much of something. A glut of gas in the marketplace can lower its price. A glut of heavy metal T-shirts in your dresser, however, has nothing to do with the economy but might be a signal that it's time to clean your room.
Glut comes from the Old French gloter, meaning "to swallow too much." The glottis is the part of your body where your vocal folds reside and where you swallow. If you go to the movies alone and get the family tub of popcorn, you are glutting yourself on the salty snack, but do try not to get any popcorn stuck in your glottis. Glut is used more commonly in reference to the economics of the marketplace, where an oversupply of one thing lowers prices.