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A will-o’-the-wisp is a ghostly light over wetlands caused by the spontaneous ignition of marsh gases, while a jack-o’-lantern is a carved root vegetable lit from within to represent a wandering soul. The two share a name in English but differ in origin: one is a natural phenomenon with a folkloric overlay, the other a crafted object with a protective purpose.
Why are will-o’-the-wisp and jack-o’-lantern confused?
The confusion dates to the 18th and 19th centuries, when English dialect dictionaries listed “jack-o’-lantern” as a synonym for the marsh light. The English Dialect Dictionary (1898) records both meanings under the same entry. A farmer in Yorkshire might say he saw a jack-o’-lantern over the bog, meaning the marsh gas. A farmer in Ireland might carve a jack-o’-lantern for Samhain, meaning the turnip lantern. The same word did two jobs, and the two traditions tangled so thoroughly that separating them now requires a look at the folklore, the science, and the practical magic each one served.
What is a will-o’-the-wisp?
The will-o’-the-wisp appears in English records as early as the 16th century. The name itself is a riddle. “Will” was a generic name for a country fellow, and “wisp” meant a handful of hay or straw used as a torch. A “Will with the wisp” was a man carrying a light, which is exactly what the marsh flame looked like: a small, bobbing torch held by an invisible hand.
The phenomenon has a physical cause. Wetlands produce methane and phosphine from decaying organic matter. When these gases rise and meet the air, they can ignite spontaneously. The flame is pale blue or greenish, low to the ground, and moves with the wind or with the gas itself. A person walking toward it will see it retreat, because the gas pocket shifts. The effect is a light that leads you deeper into the bog.
Natural philosophers knew this by the 17th century. Robert Boyle described the phenomenon in 1660 as “a shining substance” rising from marshy ground. Athanasius Kircher proposed in 1665 that the lights were caused by “fatty and sulphurous exhalations” that caught fire. He was essentially correct. The folklore absorbed the science without replacing it. People who knew the marsh gas explanation still called the light a spirit. Knowing the cause did not make the sight less eerie.
In folk tradition, the will-o’-the-wisp was not used but encountered. It was a warning. English folklore called it a “corpse candle” or a “fetch light” and believed it marked the place where someone would die. German tradition called it the Irrlicht — a soul that had not been admitted to heaven or hell. Swedish folklore named it the lyktgubbe, a ghost who carried a light and led travelers into water. For more on these related spirits, see the glossary entry on corpse candles and fetch lights.
What is a jack-o’-lantern?
The jack-o’-lantern is a deliberate object. A turnip, a beet, or a large potato is hollowed out, a face is cut into one side, and a candle or coal is placed inside. The face is not decorative. It is apotropaic: the grimace is meant to frighten away harmful spirits, or to mimic the face of the dead soul the lantern represents. The light inside is the soul itself, or a fragment of hellfire, or a warning to the living that the boundary between worlds is thin.
The practice is documented in Ireland and Scotland from at least the 18th century. Sir Walter Scott mentions “the turnip-lanterns of the peasantry” in his Letters on Demonology and Witchcraft (1830). The Irish folklorist William Wilde, in Irish Popular Superstitions (1852), describes children carrying hollowed turnips with candles on Samhain eve. The pumpkin replaced the turnip in North America because it was larger and easier to carve. The first American reference to a pumpkin jack-o’-lantern appears in an 1837 issue of the Boston Transcript.
The lantern’s origin story is tied to the figure of Stingy Jack. In Irish folklore, Jack tricked the devil and was condemned to walk the earth with only a hollowed turnip and a coal of hellfire to light his way. That story was told aloud for generations before anyone wrote it down. The first printed version appears in 1825, in the Dublin Penny Journal.
How were the two lights used in folklore?
The will-o’-the-wisp was not used. It was encountered. Folk tradition warned against following it. In English folklore, the light was called a “corpse candle” and was believed to mark the place where someone would die. In German tradition, the Irrlicht (wandering light) was a soul that had not been admitted to heaven or hell. In Swedish folklore, the lyktgubbe (lantern man) was a ghost who carried a light and led travelers into water.
The jack-o’-lantern was made. It was placed in windows, on gateposts, or at crossroads to guide the dead home or to warn them away. In some Irish traditions, the lantern was left at the edge of the village to confuse malevolent spirits into following the light away from the houses. The face was carved with specific features: a wide mouth for the spirit to speak through, or no mouth at all to keep it silent. The choice was a practical one. This practice is closely tied to the Gaelic festival of Samhain, when the boundary between the living and the dead was believed to thin. For more on that context, see our guide to Samhain traditions.
What does each light symbolize?
The will-o’-the-wisp symbolizes deception. It is a false guide, a light that promises safety and delivers danger. In moralizing folklore, it represents the soul led astray by sin, or the devil disguised as an angel of light. The 17th century preacher Thomas Fuller called it “a foolish fire, leading men into folly.”
The jack-o’-lantern symbolizes protection and remembrance. It is a light made by human hands to hold back what the dark contained. The carved face is a threshold guardian. It stands between the household and the wandering dead. The light inside is not a trick. It is a statement: we know you are there, and we are ready.
Common misconceptions
The most common mistake is treating the two as interchangeable. They are not. The will-o’-the-wisp is a natural phenomenon with a folkloric overlay. The jack-o’-lantern is a crafted object with a folkloric origin. They share a name in English because 19th century dialect lumped them together, but the traditions that produced them are separate.
A second mistake is assuming the jack-o’-lantern was always a pumpkin. It was not. The pumpkin is a North American plant, introduced to Europe after colonization. The Irish and Scottish jack-o’-lantern was a turnip, a mangelwurzel, or a potato. The turnip lantern is harder to carve, smaller, and casts a dimmer light. It is also older.
A third mistake is believing the will-o’-the-wisp is purely a superstition. It is not. The phenomenon is real, documented in scientific literature from the 17th century to the present. The folklore grew around a genuine observation. People saw lights over marshes because there were lights over marshes.
FAQ
Are will-o’-the-wisps dangerous? In folklore, yes. They lead travelers into bogs and water. In reality, the marsh gas that causes them is flammable but not actively harmful unless ignited in large quantities.
Can you make a jack-o’-lantern from a turnip? Yes. A turnip or swede is hollowed out with a knife, a face is carved into the skin, and a candle is placed inside. The walls are thicker than a pumpkin, so the light is dimmer.
Why is the jack-o’-lantern associated with Halloween? The practice dates to Samhain, the Gaelic festival at the end of October when the boundary between the living and the dead was believed to thin. The lantern was a protective object for that night.
The two lights as one story
The will-o’-the-wisp and the jack-o’-lantern are not the same thing, but they belong to the same world. Both are lights at the edge of human territory. Both mark a boundary between the known and the unknown. The marsh light is the unknown coming toward you. The carved lantern is the known pushed back against it. One is a warning. The other is a defense. That is the difference, and it is worth keeping straight.
For more on the folklore of boundary lights and wandering souls, see the full collection of folklore comparisons, which includes the differences between banshees and bean sidhe, will-o’-the-wisps and jack-o’-lanterns, and other paired spirits that share a name but not a story.