Will-o'-the-wisp

A will-o'-the-wisp, from the Latin ignis fatuus meaning foolish flame, is an atmospheric ghost light reported by travelers at night, especially over bogs, swamps and marshes. It is known by many regional names, including jack-o'-lantern, friar's lantern and hinkypunk, and folklore describes it as a flickering light that seems to mislead or guide travelers like a lantern. Modern science attributes the light to natural processes such as bioluminescence or chemiluminescence, caused by the oxidation of gases including phosphine, diphosphane and methane that are produced by the decay of organic matter in wetlands.