Oregon, on the other hand, they don't know for sure and probably never will.
This is what I found online for naming the state Oregon:
To this day there is controversy over the name of the state. World Book Encyclopedia states: The Columbia River was at one time called the Oregon or Ouragan, which means Hurricane in French. Others believe the name was derived from a mapmaker's error in the 1700s. The Wisconsin River was named the Ouisconsink and was picked up by travelers referring to the country west of the Great Lakes as Ourigan.
More knowledge of the origin of the word Oregon has surfaced in the last hundred years. Jonathan Carver may have appropriated the word, not the spelling from Major Robert Rogers. Rogers used the form Ouragon or Ouregan in a petition for an exploring expedition into the country west of the Great Lakes. This took place in London is 1765. His petition was not granted. Jonathan Carver is the first person to use the form Oregon in referring to the river of the west that falls into the Pacific Ocean. This report was published in 1778.
Neither Vancouver (1778), nor Gray (1778) used the name Oregon by any spelling during their explorations. The name was not used by Lewis and Clark nor Astor's petition to Congress in 1812. Poet William Cullens Bryant, after reading a volume of Jonathan Carver's travels mentioned Oregon in his poem "Thanatopsis" published in 1817. Pioneer travelers headed west to "Oregon, God's fertile land of plenty". So, however the name was derived or created, it stuck, and The Great Migration on the Oregon Trail had begun.
And people wonder where I come up with all this trivia knowledge I have. It's called curiousity!