The Great Clown Scare of 2016 started in the dog days of August, when a young man began wandering the streets of Green Bay, Wis., in gruesome black-and-white clown makeup, carrying black balloons. (It was later revealed that he was doing guerrilla marketing for a horror short.) A few weeks later, children in a Greenville, S.C., apartment complex told the police about clowns flashing green laser lights in nearby woods and trying to lure them with cash. The complex issued a warning to residents, but the police found nothing — not one frizzy strand of clown-wig hair.

Nevertheless, reports of sinister clowns have spread to at least 20 states, and abroad, causing school closings and several arrests. Notably, no American children have been physically harmed, though last week a man in a clown mask in Sweden stabbed a teenager in the shoulder. Law-abiding clowns are predictably upset, and have organized at least one “Clown Lives Matter” protest in response.

Creepy clown sightings aren’t new. They date from at least May 1981, when the cryptozoologist Loren Coleman coined the term “phantom clowns” to describe them. At the time, children in Brookline, Mass., were reporting clowns in vans who beckoned them with promises of candy. The police issued an all-points bulletin, established checkpoints and conducted searches, but no clowns were captured.

Still, the reports spread to at least six cities in the span of a month. Waves of sightings recurred in 1985 and in 1991 (in the latter reports the figures were often described as looking like Homey D. Clown from the TV series “In Living Color”). In each case, the stories were primarily spread by children and caused mild to moderate hysteria, but no clown predators were ever found.

The phantom clown fits the broad definition of an urban legend, a term popularized by the folklore scholar Jan Harold Brunvand in his 1981 book “The Vanishing Hitchhiker.” While urban legends are hard to define, Dr. Brunvand thinks of them as enduring rumors about improbable events, usually with a humorous or macabre element, that are spread by word of mouth.

Folklorists call them “friend of a friend” stories and argue that they survive because they offer us lessons and morals that are often tied to concerns about our transition to a modern, depersonalized society. For instance, the classic yarn about the mother who dies after finding a rat in her family’s KFC dinner is seen as a cautionary tale about the perils of eating out, while the babysitter who gets high and puts an infant in the microwave is a warning about not leaving your children with strangers.

Some folklorists align the current clown scare with other stories of “phantom attackers,” like the Phantom Slasher of Taipei from the 1950s or the Mad Gasser of Mattoon, Ill., from 1944. The latter most likely played on World War II-era fears of gas and wartime instability; in general, urban legends tend to spread in times of anxiety, when there are low levels of trust in official institutions and sources of information. Our current moment certainly qualifies.

But when did clowns become scary? It turns out that even asking that question is evidence of a short cultural memory. Dark clowns go back centuries before Stephen King. As Benjamin Radford, author of the recent book “Bad Clowns,” points out, “It’s misleading to ask when clowns turned bad, for they were never really good.”

One of the earliest antecedents of the modern clown was the 16th-century Harlequin, who wore a suit of brightly colored patches. While usually more irritating than evil, he drew on malevolent roots. One of Harlequin’s first appearances in literature is a 1585 poem that features him journeying through the underworld to spring a villainous brothel-keeper from the torments of hell. According to Enid Welsford in her 1935 study “The Fool: His Social and Literary History,” “Harlequin appears first in history or legend as an aerial specter or demon, leading the ghostly nocturnal cortege known as the Wild Hunt.” The Hunt eventually “lost some of its terrors and the wailing procession of lost souls turned into a troupe of comic demons.”

The clowns we know today have more in common with the 19th-century London pantomime player Joseph Grimaldi. Andrew McConnell Stott, the author of “The Pantomime Life of Joseph Grimaldi,” says Grimaldi is credited with adding garish makeup and exaggerated slapstick to the clown’s repertoire. Grimaldi’s personal life was racked by calamity and physical pain. He was known to joke, “I am grim all day, but I make you laugh at night.” Grimaldi died in 1837, and Professor Stott says it was Charles Dickens’s editing of Grimaldi’s memoirs that created the public’s idea of a clown who is happy on the surface but sad and self-destructive within.

Other sinister historical clowns of note include the baby-bashing, wife-beating, serial-killer clown Punch, and the murderous clown from the 19th-century opera “Pagliacci.” With stories like these, it’s a wonder clowns were ever invited to birthday parties in the first place.

Dickens was right to focus on the man behind the makeup. Most of those who have been arrested in clown costume during the Great Clown Panic of 2016 have been disaffected young men who donned the attire to cause public distress. Their age and outsider status bring to mind the Insane Clown Posse, a hugely successful (if critically maligned) “horrorcore” rap group from Detroit who wear black-and-white clown makeup and frequently use the image of the joker. Their multiplatinum albums revolve around the theme of the Dark Carnival, a fun-house purgatory where wrongdoers — often the rich and other members of the establishment — are punished. (The F.B.I. classifies followers of the group, who are known as Juggalos, as a gang, although a vast majority are peaceful.)

Knowingly or not, the band is drawing on the history of the jester as tolerated critic, a near universal role that pops up in China, Africa, and India as well as medieval and Renaissance Europe. In “Fools Are Everywhere: The Court Jester Around the World,” the scholar Beatrice K. Otto describes the court jester as the only person who could speak truth to power without consequences. He was “irreverent, libertine, self-indulgent, witty, clever, roguish” — “the fool as goad to the wise and challenge to the virtuous, the fool as critic of the world.”