1861 as a place name, originally applied by U.S. Congress to a proposed territorial division centered in what is now eastern Colorado; said at the time to mean "Gem of the Mountains" but probably rather from Kiowa-Apache (Athabaskan) idaahe "enemy," a name applied by them to the Comanches. Modern Idaho was organized 1861 as a county in Washington Territory; in 1863 became a territory in its own right and it was admitted as a state in 1890.

native people of Idaho and vicinity, and their language, from French Nez Percé, literally "pierced nose." In reference to an early custom of the people of wearing shell ornaments in pierced septums.

breed of horses favored by Indian tribes in U.S. West, 1849, either from Opelousa (perhaps from Choctaw api losa "black body") in Louisiana, or from the name of the Palouse Indians, who lived near the river of that name in Idaho, whose name is from Sahaptin palou:s "what is standing up in the water."