1868, coined from Greek helios "sun" (see sol), because the element was detected in the solar spectrum during the eclipse of Aug. 18, 1868, by English astronomer Sir Joseph N. Lockyer (1836-1920) and English chemist Sir Edward Frankland (1825-1899). It was not actually obtained until 1895; it was assumed before that to be an alkali metal, hence the ending in -ium.