Sheath Sheath Shannon's law The word sheath has a number of related meanings in English. In general usage, a sheath is any protective covering that fits closely around the object to be protected. A Sword's sheath is called a Scabbard.
There may be more than one sheath surrounding a given cable. For example, some cable designs use an inner sheath surrounded by metallic armor, over which is an outer sheath.
(Source: Federal Standard 1037C)