The will-o'-the-wisp, sometimes will-o'-wisp or ignis fatuus (moern Latin, from ignis ("fire") + fatuus ("foolish"), plural ignes fatui) refers to the ghostly lights sometimes seen at night or twilight — often over bogs. It looks like a flickering lamp, and is sometimes said to recede if approached. Much folklore surrounds the legend, but science has offered several potential explanations.