That's a bit pedantic, and in any case, the Dakota were certainly there before the Europeans or U.S. Army.
Are there records of any older names? I'd be happy to learn about them.
I think it's a salient point. Why should we be falling all over ourselves to name it what somebody else called it, especially since their presence there was pretty transitory? Based on some brief research, it looks like the Europeans have been hanging around Lake Calhoun for longer than the Dakota were.
Trying to pick "the original" name seems like an unnecessary gesture. What did the Etruscans call Rome before the Romans took it over?
One: Are, not were. There are still Dakota in MSP, and in greater Minnesota, despite the majority of the survivors of the U.S.-Dakota War being removed.
Two: You're accepting (even arguing for) the continued erasure of Indigenous identity and history from the region.
Three: While pre-contact Dakota life was not as "settled" as the Euro-American invaders, their presence and control of this area was long established, with their agricultural and hunting practices shaped to the area's particular ecosystem and having framed their religious identity to the region. Your "brief research" should have informed you that Mnirara (St Anthony Falls) and Bdote (at Fort Snelling) both were and remain sacred to the Dakota oyate.
The Dakota (as a people currently constituted) have been in Minnesota for centuries, and are descendants of the "Mississippian culture" (along with other Siouan peoples like the Dhegiha and Chiwere speaking nations) that established its presence in the area centuries before contact.
Anyway, while renaming Lake Calhoun with a name used before Europeans invaded would be a mostly insignificant gesture in recognizing the Indigenous presence in the region, it's still something. Certainly better than the lake being named after a racist POS.