god of fire and metal-work in Roman mythology, 1510s, from Latin Vulcanus, Volcanus, according to Klein a word of Etruscan origin. Often with allusions to his lameness and the unfaithfulness of his wife, Venus. As the name of a hypothetical planet between Mercury and the Sun, it is attested from 1860. French physician Edmond Modeste Lescarbault claimed to have discovered it crossing the Sun's disk in 1859. The Roman feast of Vulcanalia was on Aug. 23.