There is also a tribe called Shoshone -- not sure how it's pronounced, or much more about it, but it sounds like another possibility. Here's a description online:
http://www.newworldencyclopedia.org/entry/Shoshone
Here is just a snippet of what is said there:
The Shoshone (also spelled Shoshoni) are a Native American tribe with three large divisions: the Northern, the Western and the Eastern. The Northern are concentrated in eastern Idaho, western Wyoming, and north-eastern Utah. The Eastern lived in Wyoming, northern Colorado and Montana.
Sakajawea was the most famous member of the Shoshone, and accompanied the Lewis and Clark expedition.
