Sioux in french means 'enemy' and this is why the Sioux people actually went by Dakota or Lakota.
The Lakota, (depending on the tribe for the spelling and pronunciation), prefer not to say good bye, but rather, I'll see you soon, or "I'll see you again someday" which is spoken in an abbreviated...
Sioux
Ptecela (pronounced: pday-chay-lah)
Lila Waste (pronounced: lee-lah-wah-shday)
The Lewis and Clark Expedition Part 5/12
The Lewis and Clark Expedition Part 4/12