Vulcan n.

"being within the orbit of the planet Mercury," 1859, especially in reference to a supposed planet orbiting there (sought in vain in the eclipse of 1860), from intra- "within, inside" + Mercury (Latin Mercurius) + -al (1). The idea originated in France in the 1840s with Urbain Le Verrier, who later became director of the Paris Observatory. There was some excitement about it in 1859 when a French doctor named Lescarbault claimed to have tracked it crossing the Sun's disk and convinced Le Verrier. It was sought in vain in the solar eclipses of 1860, '68, and '69. See Vulcan.

1610s, from Italian vulcano "burning mountain," from Latin Vulcanus "Vulcan," Roman god of fire, also "fire, flames, volcano" (see Vulcan). The name was first applied to Mt. Etna by the Romans, who believed it was the forge of Vulcan. Earlier form in English was volcan (1570s), from French.

1827, "to put into flames," from Vulcan (q.v.), name of the Roman god of fire, + -ize. As a treatment for rubber, attested by 1846. Related: Vulcanized; vulcanizing.