What does the name "Idaho" mean?

It comes from Kiowa-Apache(Athabaskan) idaahe "enemy"

http://www.etymonline.com/index.php?term=Idaho

The exact origin of the name remains a mystery.

The same year Congress created Colorado Territory, a county called Idaho County was created in eastern Washington Territory. The county was named after a steamship named Idaho, which was launched on the Columbia River in 1860. It is unclear whether the steamship was named before or after Willing's claim was revealed. Regardless, a portion of Washington Territory, including Idaho County, was used to create Idaho Territory in 1863.

Despite this lack of evidence for the origin of the name, many textbooks well into the 20th century repeated as fact Willing's account that the name "Idaho" derived from the Shoshone term "ee-da-how".

The name "Idaho" may be derived from a Plains Apache word which means "enemy." The Comanches used this word to refer to the Idaho Territory.

https://en.wikipedia.org/wiki/Idaho#Origin_of_name

One of the most intriguing mysteries 0f ldaho history is the origin and meaning of the name "Idaho." The name is generally assumed to be an adaptation of an Indian word from one of the northwest tongues signifying either gem of the mountains" or "sunrise." Studies by competent
linguists reveal, however, that "Idaho" is one of many Indian "words" supplied by the white man. Research shows that "Idaho" was first considered as the name for 'he growing Pike's Peak mining area but that "Colorado" was finally chosen by Congress. It is not definitely known how
"Idaho" originated or how it reached the northwest, but it eventually replaced "Montana" for the new mining territory in the Pacific North-west when the Idaho bill was passed by Congress on March 3, 1863.

http://imnh.isu.edu/digitalatlas/geog/explore/essay.pdf

Probably made up by George M. "Doc" Willing as a practical joke; originally claimed to have been derived from a word in a Native American language that meant "Gem of the Mountains."[27] The name was initially proposed for the state of Colorado until its origins were discovered. Years later it fell into common usage, and was proposed for the state it now names.[28]

https://en.wikipedia.org/wiki/George_M._Willing