Prior to European-American establishment of the city, numerous Indian tribes had inhabited the area, including the Pawnee, Otoe, Sioux, the Missouri and Ioway. They had developed a semi-nomadic lifestyle necessary for survival on the Great Plains. The Pawnee and Otoe tribes had inhabited the region for hundreds of years by the time the Siouan-language Omaha tribe had arrived from the lower Ohio valley in the early 18th century. Translated, the word "Omaha" (actually "U-Mo'n-Ho'n") means "Dwellers on the Bluff". Usually the word is translated "against the current" but in those cases without quoting any source.