St. Erasmus, also known as Elmo, was the bishop of Formiae, Campagna, Italy. During persecution of the Christians under Emperor Diocletian he fled to Mount Lebanon and lived there for some time, being fed by a raven. His whereabouts were discovered and he was thrown into prison, from which an angel rescued him. Eventually he suffered a martyr's death. He is the member of the so called Fourteen Holy Helpers, a group of 14 saints, whose collective cult grew up in the first quarter of the 15th century.
See: Grünewald The Meeting of St. Erasmus and St. Maurice.
Nicolas Poussin. The Martyrdom of St. Erasmus.
Lives of the Saints: From Mary and Francis of Assisi to John XXIII and Mother Teresa by Richard McBrien (Author). Harper SanFrancisco, 2001.