There are three main dialects/languages (depending on how you define these rather subjective terms), which linguists refer to, often, as D-Dakota, N-Dakota and L-Dakota. Lakota (or L-Dakota) is the largest one in the west, and D in the east, and then N I think is the Yankton Sioux. D-Dakota is also called Eastern, Santee, or Woodland Sioux, and L-Dakota is also called Plains or Teton Sioux. (The term "Sioux" itself is not of Sioux origin, it's a diminutive ending in Ojibwa (aka Chippewa), in which the term for the Sioux translates, not too diplomatically, as "Little Snakes".) Dakota/Nakota/Lakota, which is the general term of self-reference for these people, means "Friends/Allies", not "Baby Serpents". It's the same word, but depending on the local form of the language the first sound varies as noted. At the time of Renville's hymnodic activity, the Lakota did not yet have Christian hymnists. He was Dakota.

Here is the text of the "Dakota Hymn" by Joseph Renville, first published 1842; I think there may be a few missing diacritics:

Wakantanka taku nitawa
tankaya qaota;
mahpiya kin eyahnake ca,
makakin he duowanca.
Mniowanca sbeya wanke cin,
hena ovakihi.

There are a couple of English translations in the (UCC, 1995) New Century Hymnal, as well as an anecdote about the hymn's prominence in the history of the Dakota people (where it played a role in a way analogous to that of "Amazing Grace" in the history of the Cherokee). I'll try to transcribe these, that is, I'll try to remember to do so next time I have my NCH at hand.