I saw "Potomac" floated which has a pretty good ring to it.
Yesterday, I floated (river pun!) "Patoma" to the wife. No "c". Official state song can be "Return of the Mac"
That's actually... really nice. I like that. It's also a Native American word, so goes along with the Dakotas and other states using indigenous words, so there is precedent, as well as states being named after their geographic features, like Mississippi.
Yeah of all the names I've seen legitimately floated, it's been my favorite. Not the mouthful that some of the others are, and it just sounds good and stately, beyond the benefit of honoring natives to our country, which would be excellent if we honored them by giving our country's capital a native name of sorts. It works on a lot of levels.