What is "syilx"

The Okanagan people, also spelled Okanogan, are a First Nations and Native American people whose traditional territory spans the U.S.- Canada boundary in Washington state and British Columbia in the Okanagan Country region. They call themselves the Syilx , a term now widely used. They are part of the Interior Salish ethnological and linguistic grouping. The Okanagan are closely related to the Spokan, Sinixt, Nez Perce, Pend Oreille, Secwepemc and Nlaka'pamux peoples of the same Northwest Plateau region.