This is another of those things that makes me remember why I got into historical linguistics; Lameen Souag posts about a wonderful resource that’s finally online:
A key document in Native American philology which has been circulating in samizdat form for decades is finally online and searchable: the multi-authored Comparative Siouan Dictionary (as noted by Guillaume Jacques). Named for the last of its speakers to resist colonization, the Sioux or Lakota, the Siouan family was spread over a vast section of North America, covering much of the Missouri and Mississippi valleys but with old outliers as far east as Tutelo in Virginia. The names of several Midwesternstates derive from Siouan languages, so they make a convenient starting point for exploring the database. Minnesota is from Dakota mni sota “cloudy water”,both elements of whose history you can trace back here to proto-Siouan: *waRé• “lake, water” and *(a)só•tE “hazy, bluish, cloudy”. *waRé• also yields Chiwere ñį, which in combination with the Chiwere reflex of *parás-ka “spread > flat (1)” yields the name of Nebraska. Dakota, from a name of the Sioux, has a less venerable history, being traceable only back to proto-Mississippi Valley Siouan *hkota/*hkoRa/*hkora “friend”, with unexplained internal variation and similar forms in other families suggesting the possibility of a loan. (The la- element might have something to do with fire; see John Koontz’s discussion.)
Just looking at those lists of cognates makes me want to start learning the languages!