"Jack has been a general term for a boy since the 16th century, and the British can claim ownership of the original use of the phrase jack-o’-lantern. In the 17th century, it referred to a night watchman, a man who literally carried a lantern.
But, it was also a nickname for strange, flickering lights seen at night over wetlands or peat bogs and mistaken to be fairies or ghosts. This natural phenomenon is also called ignis fatus, which means “foolish fire,” friar’s lantern, and will-o’-the-wisp ..."