The nickname associated with White Castle’s small hamburgers is “slider.”
A slider is a small hamburger or sandwich, commonly served on a small bun. The term became strongly associated with White Castle, whose compact square hamburgers were inexpensive and designed to be eaten quickly. White Castle helped establish the small hamburger as a recognizable fast-food format in the United States.
The exact origin of the word is debated. One explanation connects it with the ease of sliding the small, greasy sandwiches down the throat; another links it to the way the sandwiches slid across a griddle or were handled in restaurants. “Slider” is now used more broadly for small sandwiches made with beef, chicken, pork, or other fillings.
A slider is defined by its small format, not by one mandatory topping or cooking method. White Castle’s hamburger is therefore a famous example, but the word is no longer exclusive to that chain.