Jessica, you wrote asking for the Sioux name for the Black Footed Ferret.
There are three dialects in this language: the Teton, the Yankton, and the
Santee.  Words vary slightly (consonant clusters) from one dialect to
another.  I'll give you the words from the Teton Sioux (Lakota).
 
The Lakota call the Blackfooted Ferret: Itopta Sapa.  This is a shorthand
way of saying Ite Opta Sapa, which means "Black (stripe) Across the Face.
The ferret is sacred (wakan) because it is so hard to kill.  It is believed
that anyone who kills a ferret will soon die himself.  That is why it's "bad
luck" to kill one.  To pronounce the name, you would say "eetoptah shahpah"
or in the long version, "eetay optah shahpah."
 
To compare with the Blackfoot, the Blackfoot name for the Black Footed
Ferret is: Omachk Apao, which means "Big Weasel." (The ermine or winter
weasel is called: Apao).
 
Related Words in Lakota (the capatalized N's are nasalized, not pronounced):
Weasel:  ItuNkasaN or ItuNkasaNla
Mink:  IkusaN or IkusaNla
Otter:  PtaN or (the sacred name) HepaN
 
Related Words in Blackfoot:
Summer (Brown) Weasel:  Otao
Mink:  Soyekaye ("Water on its Back")
Otter:  Emonissi  (Referring to how it glides around & is hard to approach
on land)
 
There is an interesting article by John Ewers in the Plains Anthropologist
(vol 22, #78, 1977) which discusses the use of weasel skins and the
symbolism of weasels on the Plains: "Notes on the Weasel in Historic Plains
Indian Culture".  You can probably find this at your closest university
library.  Nothing about the Black Footed Ferret, but you might find it
interesting anyway.
 
Good Luck on your paper!
 
Isabel Two
[Posted in FML issue 1724]