As you know if you've read my little info box on the right side of this page, I currently live in Missoula, Montana. The derivation of the word name "Missoula" is somewhat opaque, but is generally agreed to derive from the Flathead (Selish) word nmesuletkʷ. However, not everyone agrees on the meaning of this word. I have heard perhaps most commonly from white people and historians "river of ambush/surprise", and from Native people "icy water", referring to glacial lake Missoula. Naturally I'm inclined to give more credence to the latter (though of course indigenous people are just as prone to folk etymologies as we Euro-Americans are). After doing some research it seems that my hunch was justified.
The easiest part of nmesuletkʷ to deconstruct (for a non-speaker of Salish) is the suffix -etkʷ, which means "liquid", often specifically in the sense of "water" in place names, cf. ntx̣ʷetkʷ, 'river'. The nmesul- part is a bit harder, but there are clues in several of the Salishan languages. The root sul seems to mean "cold" or "frozen": slsulčsti, 'his hands are freezing'; suł, 'froze'; cf. Spokane sul, 'cold'. The initial n- is presumably the locative marker present in many Salishan languages, including Spokane and Okanagan. The me- is the only part for which I was able to find an unequivocal answer, but may be a stem formative cognate with Okanagan -m-. So a rough translation would presumably be something like "place of the frozen water", quite likely a reference to glacial lake Missoula.
Jerome Stueart interview (pt. 3)
6 days ago