The static electric discharge known as St. Elmo’s Fire gets its name from St. Erasmus, the Bishop of Formia, Campagna, Italy. Erasmus — or Elmo, as his name sometimes passes into English — was martyred by being disemboweled during the persecution of Diocletian (c. 303). Sailors invoked his protection, and considered the blue electrical discharges which would sometimes appear on the masts or riggings of their ships as a sign of his protection. The phenomenon, which can occur naturally, eventually came to bear his name: St. Elmo’s Fire. St. Erasmus’ feast day is June 2.
Saints Erasmus and Maurice, by Matthias Grünewald (source)
