Ignis fatuus

WORD OF THE DAY

ignis fatuus / noun / IG-nis FATCH-uh-wus

Definition
1: a light that sometimes appears in the night over marshy ground and is often attributable to the combustion of gas from decomposed organic matter
2: a deceptive goal or hope

Examples
"The flickering lights that led superstitious voyagers astray are not mere legends. So-called ignis fatuus, or 'foolish fire,' is a real phenomenon: a ball of flame that hovers above a marsh’s dark, still water for a few minutes before dissipating into the night."
— Benji Jones, Popular Science, 31 Oct. 2018

The story also helped explain ignis fatuus, a natural phenomenon that occurs in marshlands and bogs—such as those in Ireland’s countryside—producing flickering lights as gases from decomposing organic matter combust.
—National Geographic, 27 Oct. 2020

Did You Know?
Ignis fatuus is a Latin term meaning, literally, "foolish fire."
Other names for this light are jack-o'-lantern and will-o'-the-wisp—both of which are connected to folklore about mysterious men, Jack and Will, who carry a lantern or a wisp of light at night.
A Scottish name for ignis fatuus is spunkie, from spunk, meaning "spark" or "a small fire."
It has also been told that ignes fatui (the Latin plural form) are roaming souls.
No doubt these stories spooked listeners by candlelight, but in time, advancements in science not only gave us electricity to dispel the darkness but proved ignis fatuus to be a visible exhalation of gas from the ground, which is rarely seen today.