MINNEAPOLIS (WCCO) - “Trick or treating” has become one of America’s favorite past times, with billions of dollars going into just one night.

Long ago, there was more to trick or treating than just free candy. In fact, it was quite literally a matter of life or death.

History buff and Argosy University psychology professor Bill Forisha says the door-to-door tradition was started among the Celtic people around the Middle Ages.

“Lots of ancient people thought that there was a transition time after you die, you know, hanging around,” Forisha said.

The tradition happened around their new year, November 1 – the time when the dead spirits were supposed to leave. But when they didn’t, that’s when the poor would make a visit to the rich.

“They end up bargaining, ‘I’ll pray for the dead in your family if you give me a soul cake,’” he said.

So people were actually praying and paying for the dead to move along.

It’s also the spirits we have to blame for why we dress up when we go door to door. Although back then it wasn’t dressing up as a sexy French maid – it was dressing up as the evil spirits themselves.

“They’d dress up as spirits and try to make life difficult for the spirits so they’d move on,” he said.

And that brings us to the trickery part of this equation.

Forisha says the notion of tricks changed when the Irish migrated to the US in the 1840s, bringing the tradition with them. Whereas before it was threatening the dead to move on, now it’s a bit different.

“Present day reality: I’ll trick you if you don’t give me something – Extortion. Both really positive thoughts aren’t they,” Forisha said.