The name of the river comes from the Spanish word, "amargo", for "bitter", probably shortened from "agua amargosa", "bitter water". The name was first recorded in 1844 and is believed to refer to the alkaline water. The river is an ancient stream, following an antecedent canyon. Evidence of human habitation along the river goes back more than 10,000 years. In addition to prehistoric Lake Manly in Death Valley, the middle river valley was submerged during the late Pleistocene by prehistoric Lake Tecopa.