Mississippi is a southern state of the United States. Postal abbreviation: MS. Official (long) name: State of Mississippi. The state takes its name from the Mississippi River, which flows along the western boundary. The name itself probably comes from Native American words with various spellings that mean "large waters" or "father of the waters." Other nicknames attached to Mississippi are the Magnolia State and the Hospitality State. USS Mississippi was named in honor of this state.