The expression 'drinking the Kool-Aid' was coined from a horrifying tragedy that happened 40 years ago today

"Drinking the Kool-Aid" is a phrase bandied about regularly in corporate life, especially when someone wants to take a dig at people with a cult-like belief in a business philosophy or those fanatically chasing an idea that will end badly.

But few realise the etymology of the expression and the tragedy it came from.

This Sunday, November 18, marks the 40th anniversary of the mass murder-suicide of more than 900 people, most of them Americans who were members of a California-based cult called the Peoples Temple of the Disciples of Christ, run by the reverend Jim Jones.

It became known as the Jonestown massacre. Until 9/11, it was the largest loss of American citizens in a single incident.

His "church" formed in the 1960s with Jones presenting himself as a faith healer and sage able to protect his followers from a nuclear armageddon. His following grew through the '70s, to thousands of followers with churches in LA and San Francisco. Initially he was feted by politicians for his utopian ideals, not realising that behind the charisma, they were dealing with a paranoid figure with Communist sympathies.

But by 1977, there were growing concerns about Jones and the way he treated his followers, and as media pressure from exposes of beatings and financial impropriety grew, he fled with hundreds of them to a farm compound he'd been building in the South American nation of Guyana, 150 miles northwest of the capital, Georgetown.

He called it Jonestown.

Growing concerns about the treatment of US citizens, and whether they were being held against their will in Jonestown led a US Congressmen, Leo Ryan, with reporters in tow, to head to the compound to investigate in November 1978.

It didn't go well.

Ryan visited on 17 November, and as he was leaving the following day, more than a dozen cult members jumped on their truck, seeking to defect to the USA. They made it to the airstrip to fly back to the capital, Georgetown, however, a group of cult members who accompanied them opened fire on the planes, killing Congressman Ryan, and four others, photographer Greg Robinson from The San Francisco Examiner, cameraman Bob Brown and NBC journalist Don Harris, as well as Temple defector Patricia Parks. Another 11 people were wounded.

Peoples Temple member Larry Layton, who led the shootings at the airstrip, was convicted in 1986 of conspiracy to murder Ryan and aiding and abetting in the attempted murder of Richard Dwyer, a US diplomat wounded in the attack. He was the only cult member charged and was released from jail in 2002.

But the shooting attack that day led cult leader Jim Jones to implement a mass suicide/murder plan he dubbed “revolutionary suicide”.

He'd made a fruit cocktail laced with cyanide and valium, and didn't use Kool-Aid, but rather a cheaper alternative called Flavor Aid to hide the bitter poison.

Cult members were made to poison their children first, then themselves. Many found with bent needles in their arms suggest they were murdered by followers who forcibly injected them.

When Guyanese authorities finally made it to the jungle compound, they were confronted by the overwhelming stench of 918 dead people, including 304 children.

Jones died from a gunshot wound. Less than 100 of the Temple members survived.

Four decades later, the jungle has resumed Jonestown. His legacy is a phrase at times used glibly, but with a chilling history.

A warning: the photo below is shocking, but we've included it as a reminder of the horror that came from "drinking the Kool-Aid".