Why everyone suddenly wants to know their Enneagram personality number.

It's been around for seven decades, but thanks to a slew of influential celebrities, the idea of the Enneagram is back.

Creator of The White Lotus, Mike White, had every cast member take the test before they filmed in Thailand. He then "diagnosed" each character by the Enneagram, too. (Spoiler: Leslie Bibb and her character, Kate, were both a 1).

Amy Poehler is reportedly into it, making all her friends take the test, including Maya Rudolph and Tina Fey. It was Tina who said it was more accurate than horoscopes (she's a 3 by the way). Glennon Doyle just admitted she was a 4 in her latest newsletter. So what actually is the Enneagram test?

Watch: No, we're not ready to stop talking about The White Lotus yet. Post continues below.

Put simply, it's a personality test where you are classified as a number. This number is interconnected with others on the Enneagram (that's a nine-pointed "shape", by the way, invented by ancient Greeks — think Pythagoras). Your number is supposed to reveal your motivations, priorities, dominant characteristics and even fears.

And Aimee Lou Wood said Mike White was "obsessed with it", telling the Hollywood Reporter, "We all wanted Mike's affection and his approval, even though he's usually the most chill person on set, everyone did the test. And then everyone was like, 'Oh God, have I got a bad number? Have I got one that Mike doesn't like? Oh God, oh God.' Everyone was so nervous to tell Mike what our number was, which was so funny."

The good news is the numbers only go up to 9, so you can really only be one of nine personalities. That's fewer numbers than astrology! However, you can be a blend of one or two numbers, hence the Enneagram points.

Where does the Enneagram test come from?

The origin of the test is murky, but the original shape reportedly dates back to the Armenian philosopher George Ivanovich Gurdjieff, who reintroduced it as a cosmic spiritual guide in the early 1900s when mysticism was having a moment. It popped up again in the 1950s when a Bolivian philosopher and spiritual teacher named Oscar Ichazo formulated the bulk of it. Post World War II was a boom time for spiritual and psychological exploration, including, ahem, cults. 

People were prosperous, and loads of them were traumatised, or at the very least, disillusioned by the war. (This is when Scientology first gained a foothold in mainstream discourse, by the way). Ichazo had his own Institute, which he expanded to the United States in the 1970s — another period of time when pop psychology and soul journeys were gaining traction.

Ichazo's protégé, Claudio Naranjo, took his version to Berkeley, California, (naturally, given its reputation as a free-thinking hippie hub) and taught loads of people, including two Jesuit priests, who used it as a tool in Christian teachings before it was used in larger experiments in Stanford University.

The rest is history. 

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Critics call the Enneagram test pseudo-scientific, but in this crazy world where almost nothing is as straightforward as it once was — including dating, housing, the cost of living, having babies — isn't it comforting to be able to identify someone by a number (or two)?

It's been expanded upon, turned into systems and "programs". In other words, it's kind of become its own religion. But, a quick quiz is all it takes to diagnose yourself, your potential partner or — gulp — your boss.

Here's a brief overview of each of the personality types. But if you're curious, you can take a free quiz here.

The nine Enneagram types, explained.

Type 1: The Reformer/Perfectionist

Basic desire: Goodness, integrity

Worst traits: Hypocrisy, anger

Type 2: The Helper/Giver

Basic desire: To feel worthy of love

Worst traits: Manipulation, self-hatred

Type 3: The Achiever/Performer

Basic desire: To feel valuable

Worst traits: Need to be the best

Type 4: The Individualist/Romantic

Basic desire: To be uniquely themselves

Worst traits: Dissociation, daydreaming

Type 5: The Investigator/Observer

Basic desire: To understand everyone and the world

Worst traits: Intellectualising instead of changing

Type 6: The Loyalist/Loyal Sceptic

Basic desire: To have support and guidance

Worst traits: Indecision and doubt

Type 7: The Enthusiast/Epicure

Basic desire: Contentment and safety

Worst traits: Feeling like it's never enough

Type 8: The Challenger/Protector

Basic desire: To gain influence

Worst traits: Believing they are fine on their own

Type 9: The Peacemaker/Mediator

Basic desire: Connection

Worst traits: Avoiding tough conversations

Feature image: Getty.