tinfoil hat

In the 19th century, a tinfoil hat was a kind of party hat. The phrase took a turn, though, in the 20th century. A 1920s sci-fi short story, “The Tissue-Culture King” by Julian Huxley, featured characters wearing “caps of metal foil” to evade mind-control waves.

Huxley’s headwear illustrates the core concept of the tinfoil hat: It acts as a kind of Faraday cage to block various kinds of electromagnetic waves. We can find the specific phrase tinfoil hat in the 1980s, by which time it had become associated with individuals who would wear them in the belief they would protect them nefarious rays seeking to surveil, brainwash, or otherwise influence them.

In the 1980–90s, tinfoil hat became a shorthand for a “conspiracy theorist”—you know, JFK, moon landing, and later, 9/11 truthers. A 1997 internet commenter observed that tinfoil hat was “the oldest insult” on Usenet.

Nevertheless, the tinfoil hat became a full-fledged trope in popular media in the 1990s–2000s. In a 1999 episode of The Simpsons, Bart becomes a paranoid conspiracy theorist wearing a tinfoil hat because he fears Major League Baseball was spying on everyone. Spoiler alert: He was right.

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In the 2002 film Signs, Mel Gibson’s character and his family don tinfoil hats to keep aliens from reading their minds. (Too bad it wasn’t effective at blocking racism and antisemitism, though.) In the late 1990s and 2000s, the cartoon Futurama regularly featured a tinfoil hat-wearing character with some really far-out—veritably cosmic—prophecies.

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Musician Weird Al included a verse riffing on tinfoil hats and conspiracy theories in his 2014 parody song of Lorde’s “Royals,” called “FOIL.” 

In a 2015 episode of the TV show Better Call Saul, a character wraps himself in space blankets to shield him from electromagnetic radiation; he’s threatened with being committed to a mental hospital.