Contrary to popular belief, the now universal marijuana-culture shorthand 420 — the basis of today's April 20th unofficial National Weed Day high holiday — has nothing to do with police codes, Bob Dylan, tea time in Amsterdam or what hotel room the Grateful Dead liked to stay in.

It started with a group of five friends, athletes at San Rafael High School back in 1971, dubbed the Waldos because they hung out near a wall on the edge of campus.

According to Ryan Grim in a report for The Huffington Post, the Waldos were tipped off that a Coast Guard member had a pot garden in the woods near the Point Reyes Peninsula Coast Guard station. Armed with a vague treasure map in hand, they agreed to meet after practice at the school's statue of Louis Pasteur, at exactly 4:20 p.m.

"We'd meet at 4:20 and get in my old '66 Chevy Impala and, of course, we'd smoke instantly and smoke all the way out to Pt. Reyes and smoke the entire time we were out there," an original Waldo member named Steve told Grim. "We did it week after week. We never actually found the patch."

Shorthand for their herbal treasure hunts soon emerged. The Waldos say they originally called the meeting 420-Louis, but that it eventually dropped to 420, and they have a 420 flag and references in postmarked letters to stake their claim — enough to convince The New York Times and urban-legend-buster snopes.com of the veracity of their claim.

Unsurprisingly, the Waldo's found their secret code incredibly useful, and continued to use it long after their search meetings ended. "I could say to one of my friends, I'd go, 420, and it was telepathic. He would know if I was saying, 'Hey, do you wanna go smoke some?' Or, 'Do you have any?' Or, 'Are you stoned right now?' It was kind of telepathic just from the way you said it," Waldo Steve said in The Huffington Post. "Our teachers didn't know what we were talking about. Our parents didn't know what we were talking about."

But instead of remaining a local stoner lingo, the term took on a life of its own when counterculture legends The Grateful Dead moved to San Rafael from San Francisco. Several of the Waldos had connections to the band — one's father was a groundskeeper for them, another had a brother who managed one of the Dead's side bands, Too Loose To Truck, and several of the Waldos would hang out at Dead parties and rehearsals. No one recalled saying 420 around the band to Grim, but the phrase some how made its way through the fervent Grateful Dead subculture over the next two decades.

It was outside a Dead concert in December of 1990 when High Times reporter Steven Bloom first heard the term. A flyer in the hippie-central parking lot read "We are going to meet at 4:20 on 4/20 for 420-ing in Marin County at the Bolinas Ridge sunset spot on Mt. Tamalpais," and continued with a half-correct explanation, "420 started somewhere in San Rafael, California in the late '70s. It started as the police code for Marijuana Smoking in Progress. After local heads heard of the police call, they started using the expression 420 when referring to herb — Let's Go 420, dude!"

(According to Snopes, no police department has ever used radio call code 420 for anything, much less a marijuana-related offense.)

With Bloom's discovery of 420 published in 1991, the term soon went global. Several clocks in Pulp Fiction read 4:20. The scoreboard in Dazed and Confused showed the score to be 42-0. And the act that codified the legalization of medical marijuana in California was issued as SB420.

April 20 is the official unoffical pot smokers' holiday, where thousands show up at 420 rallies today on college campuses like the University of Colorado-Boulder and University of California-Santa Cruz — the latter less than 90 miles from the original Louis Pasteur statue that was the starting point of it all.