The Siouan language is a Native American language family that is spoken by several tribes in the Great Plains region of North America. The three crossword solutions for the term 'Siouan tongue' are Osage, Teton, and Omaha. The Osage Nation is a Midwestern Native American tribe that traditionally spoke the Osage language, which is a Siouan language. The Teton Sioux, also known as the Lakota, are a Native American people who traditionally spoke the Lakota language, which is a Siouan language. The Omaha people are a federally recognized Midwestern Native American tribe who traditionally spoke the Omaha-Ponca language, which is also a Siouan language.