THE NAME "jack-o'-lantern" is of British origin and dates from the 17th century, when it literally meant "man with a lantern" (i.e., a night watchman). It was also a nickname for the natural phenomenon known as ignis fatuus (fool's fire) or "will o' the wisp," the mysterious, flickering lights sometimes seen at night over wetlands and associated in folklore with fairies and ghosts playing pranks on travelers.
Over time "jack-o'-lantern" became the popular term for a homemade object also known as a "turnip lantern," defined by Thomas Darlington in his 1887 volume The Folk-Speech of South Cheshire as "a lantern made by scooping out the inside of a turnip, carving the shell into a rude representation of the human face, and placing a lighted candle inside it."
In some parts of Great Britain carrying turnip lanterns was regarded as a form of pranksterism. Darlington writes: "It is a common device of mischievous lads for frightening belated wayfarers on the road." For Catholic children it was customary to carry jack-o'-lanterns door-to-door to represent the souls of the dead while begging for soul cakes on Hallowmas (All Saints Day, Nov. 1) and All Souls Day (Nov. 2). They were also carried by parading celebrants on the night of Guy Fawkes Day (Nov. 5).
According to a popular legend which was surely created after the fact, the jack-o'-lantern took its name from a roguish Irishman known as Stingy Jack, who tricked the Devil into promising he wouldn't end up going to hell for his sins. When Jack died he found out he had been barred from heaven as well, so he journeyed down to the gates of hell to demand his due. Wouldn't you know it, the Devil kept his promise by dooming Jack to wander the earth for all eternity with only an ember of hellfire of to light his way. Thenceforth, the legend says, he was known as Jack O'Lantern.
It wasn't until Irish immigrants brought the custom of carving jack-o'-lanterns to North America that the more commonly available pumpkin came to be used for that purpose, and not until the mid-to-late 19th century that pumpkin carving became a Halloween staple across the United States.
More Halloween Customs
• Why Do We Bob for Apples on Halloween?
• Why Do We Wear Costumes and Go Trick-or-Treating?
• Is Halloween Candy Tampering a Myth?
• A Quick Guide to the Origin and History of Halloween
• History of the Jack-O'-Lantern - History Channel
• Turnip Battles with Pumpkin for Halloween - BBC News
• The Legend of Stingy Jack - Novareinna.com
• Hallowe'en - The Dew-Drop: A Monthly Magazine For The Young, 1873
• Jack O'Lantern - Transactions of the American Philological Association, Vol. 26, 1895