helium (n.)

1868, coined from Greek hēlios "sun" (from PIE root *sawel- "the sun"), 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; before then it was assumed to be an alkali metal, hence the ending in -ium.