Mattermouth is a portmanteau of matter and mouth. It is also a pun of motormouth. Matter is a physical substance that is made out of matter, it can be found anywhere on earth. Matter derives from Middle English by way of Old French from Latin. Materia is Latin for timber and substance. Mater means mother in Latin. Mouth is the cavity of the lower part of the human face. It derives from the Old English word mūth of a Germanic origin, Dutch word mond and German word Mund.
Mattermouths made their debut in Super Mario Galaxy 2, where Mario can find them in places such as the Haunty Halls Galaxy and Bowser's Lava Lair. If he falls into the hole Mattermouth creates as he destroys the ground, Mario will lose a life. Mattermouth will turn around if you stomp on his head as he is travelling, though this is risky. Mario will also lose some of his health if he touches these enemies elsewhere, such as getting caught in their path.
Mattermouths made their latest appearance in Mario Party: Island Tour. The minigame Tragic Carpet Ride involves these enemies tearing away at a carpet with their feasting, hence the game's name. The players have to stand on the carpet's remains to score points (1 point per second). If they fall, they stop earning points. Whoever has the most points at the end (that is, the one who survives the longest) wins. Mattermouth will also stun anyone he collides with in this game.