Knackwurst

Knackwurst (in North America sometimes spelled knockwurst (listenⓘ) refers to a type of sausage of northern German origin from the mid-16th century. The many available varieties depend on the geographical region of their production. The German noun Knackwurst—which, in English, is sometimes corrupted as knockwurst—comes from the German verb knacken (listenⓘ) ("to crack") or the adjective knackig (listenⓘ) ("crisp"). This refers to the swelling of the sausage during the process of cooking, so that the skin becomes pressurized and balloon-like, and tends to "pop", often exploding the juices, when bitten into (authentic example: listenⓘ). (Cf. the British term "banger".) The term ″Knackwurst″ came up in Germany the middle of the 16th century. In Germany, all different kinds of Knackwürste are abbreviated Knacker (listenⓘ).

Source: Wikipedia