"Drinking the Kool-Aid" is an expression used to refer to a person who believes in a possibly doomed or dangerous idea because of perceived potential high rewards. The phrase typically carries a negative connotation. It can also be used ironically or humorously to refer to accepting an idea or changing a preference due to popularity, peer pressure, or persuasion. In recent years, it has evolved further to mean extreme dedication to a cause or purpose, so extreme that one would "drink the Kool-Aid" and die for the cause.
While use of the phrase dates back to 1968 with the nonfiction book The Electric Kool-Aid Acid Test, it is strongly associated with the events in Jonestown, Guyana, on November 18, 1978, in which over 900 members of the Peoples Temple movement died. The movement's leader, Jim Jones, called a mass meeting at the Jonestown pavilion after the murder of U.S. Congressman Leo Ryan and others in nearby Port Kaituma. Jones proposed "revolutionary suicide" by way of ingesting a powdered drink mix made from Flavor Aid (later misidentified as Kool-Aid) that was lethally laced with cyanide and other drugs.