A derogatory term used to call "beach people" or people who live on the beach or on the coast. The word originated from the movie "The Little Mermaid" and has since migrated into a foul term used to call the locals in a beach or coast city. It generally can mean a few things, such as: moron, bum (beach bum), low life, it also can refer to them as being stuck up or ignorant.
Customer: "excuse me miss, what kind of candy do you have in this store?"
Beach lady: "All we have is salt water taffy, what else is there?"
Customer: "omg you are such a dinglehopper."
Person 1: "Oh hey Jim, how have you been?"
Jim: "Good, just got back from my giant beach house 6 months ago."
Person 1: "God you're such a dinglehopper."