In the early 19th century, the valley was inhabited by the Atfalati, a hunter-gatherer Kalapuyan band that spoke a dialect of Northern Kalapuyan. In the middle 19th century, the Atfalati lived in several villages in the valley, including Chakeipi ("Place of the Beaver", translated by early white settlers as "Beaver Dam"). Early Euro-American settlers called the valley the "Twality Plains", a corruption of the name of the Atfalati tribe. Other early variations included Falatin, Nefalatine, Twalaity, and Quality, with each roughly translated as slow river to describe the Tualatin River, or may translate as land without trees.