Located near Bonk, the Schmaltzberg fat mines are an important source of fat for Uberwald, as well as for the rest of the Disc. Presumably, they are the remnants of the Fifth Elephant, one of the world-bearing elephants of Discworld who, sometime in the distant past, was knocked off the shell of A'tuin and went into orbit around the Disc, eventually colliding with it, seeding it with metals and flame broiling existing animals at the time, which over time became the fat deposits. The Schmaltzberg is also the name of the great underground city of the Dwarfs, accessed through guarded surface gates in Bonk and connected by a shared railway terminal. It is discussed in greater detail in The Compleat Discworld Atlas as the underground more-than-half of the Bonk-Schmaltzberg conurbation.
On Roundworld, Schmaltz refers to kind of pork, chicken or goose fat often used as a bread spread in German and Polish cuisine. "Schmaltzberg" literally means "Fat Mountain" in German.