The origins of April Fools' Day, known for its tricks and pranks, are rather murky.
One likely explanation is April Fools was "a hazing ritual" to welcome spring, said Alex Boese, curator of the website Museum of Hoaxes.
Many cultures celebrated the beginning of the new season with "mischief, misbehavior or deception," Boese told USA TODAY Network.
"Pranks are very much associated with the start of new things," he said.
That's true even today. Think about hazing freshmen at colleges or playing pranks on the new guy at the office, he said.
The earliest connection of April 1 to playing tricks is documented in a 1561 poem by Flemish writer Eduard de Dene, Boese said. According to the Museum of Hoaxes site, in the poem a nobleman sends his servant on absurd errands on April 1.
The poem's reference to April Fools' Day is so clear that it suggests this tradition was well-established in the Netherlands by the mid-16th century, Boese said.
Another theory is April Fools' Day began when France switched from the Julian to the Gregorian calendar, which moved the New Year from around April 1 to Jan. 1. The story goes that people made fun of those who had stuck with the old calendar.
Boese disagrees with this theory, pointing out that the French calendar reformation was in the late 1500s — after the Flemish poem was written. Also, the French never celebrated New Year's on the exact date of April 1, he said.
Fake origin story
One made-up story comes from Boston University professor Joe Boskin. In 1983, the Associated Press called Boskin for an interview about how April Fools' Day started.
Boskin told the reporter he didn't know. The reporter insisted Boskin not be so modest, Boskin said in an interview with USA TODAY.
So, Boskin made up a story about how April Fools' Day began in the 5th century, when King Constantine's jesters organized a union and demanded one jester be allowed to be king for the day.
The king for the day would be known as "King Kugel" — named after the traditional Jewish pudding dish.
"I was expecting him to say, 'Truly, you're putting me on,'" Boskin said. "But he said, 'How do you spell that?'"
The AP published the story, and Boskin got calls from other news outlets wanting interviews about the holiday's origins.
When the AP discovered the story was false, they called Boskin, furious.
"They said I lied to them," Boskin said. "I said, 'I lied? How can you lie on April Fools' Day?'"