The Shady Story of How “Idaho” Got its Name
The name "Idaho" was originally going to be the name of what is now Colorado. Boise Dev notes, "In 1860 when Colorado needed a name, mining lobbyist George M. Willing presented the name “Idaho” to Congress, claiming it was a Native American Shoshone word meaning “Gem of the Mountains.”
No one really knows where George got the name or how or why he decided to come up with it but what we do know is there is no Native American word like he claimed. It was not until after Congress agreed to use the name that they realized it was a made up word.
“People tried to find Nez Perce, Shoshoni, Yakima and Arapaho words that sounded like ‘Idaho,’ but they never really got anywhere. They were looking for a (Native American) word that never really existed.” - The Idaho Historical Society
Boise State Public Radio notes, "shortly before the name was to be ratified, lawmakers discovered it was a fraud. At the very last minute, Idaho was pulled from that bill and it became Colorado Territory instead.”
When the states were being formed they all needed names, many stemming from Native American words. Even though they realized that this one "Idaho" was just a made up word, congress, who years earlier already decided to do something different for Colorado and used a Spanish name - didn't have any new ideas or plans for a name for Idaho. So they decided to go for it. So Idaho it was.
There are a few other tidbits out there for where "Idaho" came from. According to Digital Atlas, "The name "Idaho" was used for a steamship which traveled the Columbia River. With the discovery of gold on the Clearwater River in 1860, the diggings began to be called the Idaho mines. "Idaho" is a coined or invented word and, despite popular folklore, is not a derivation of an Indian phrase "E Dah Hoe (How)" supposedly meaning "gem of the mountains."