Cesium was discovered by German chemists Robert Bunsen and Gustav Kirchhoff in 1860. They identified cesium as a new element using their invention, the spectroscope, by analyzing the blue lines in the emission spectrum of mineral water from Dürkheim, Germany. The element was named "cesium" from the Latin word "caesius," meaning sky blue, referring to the characteristic blue lines seen in its spectrum. Although Bunsen and Kirchhoff discovered the element, the pure metal was first isolated later by Carl Theodor Setterberg in 1882.