What do Isabella Blow, Valentino, Lady Gaga—and most recently, Jonathan Anderson’s Dior—all have in common? They’ve all been given the word treatment through famed milliner Philip Treacy.

“A hat is a mood. It’s a feeling,” Treacy tells me on the eve of the Dior Cruise show. Last week, Anderson teased the Los Angeles-based presentation with a custom pair of the milliner’s “Hat” hats—this time, proclaiming “Dior.” Little did we know it was just the beginning of Dior’s new hat vocabulary.

The famed word hat first started with Treacy’s own couture line: In 2001, he got the idea to create a hat out of feathers that cheekily read “Hat.” Made of Japanese Yokohama chicken feathers, each hat takes three days in total to sculpt, shape, bake, and assemble (Treacy’s friend, the late designer Anthony Price, raised the chickens and harvested the feathers for him). “You really get to know every single feather you’re working with. You have to discover which feather will give you which letter; it all has to do with its spine. But every letter presents a different challenge,” Treacy says of the overall experience. “Feathers don't levitate on the head on their own. Or very easily.”

It wasn’t long before the Hat hat got its Vogue debut. Britney Spears was the cover of Vogue’s All-American November 2001 issue (the first issue produced post 9/11), shot by Herb Ritts. Inside, the opening photo of the story was a black-and-white shot of the pop star wearing her very own Treacy word hat (commissioned by Anna Wintour), exclaiming her name.

“Of course, when Isabella saw Britney’s hat, she was absolutely furious,” Treacy reflects with a laugh. “She wanted Blow on hers, because she was doing a collaboration with M.A.C. and they designed a lipstick for her called ‘Blow.’” The next year, Valentino Garavani asked Treacy to create a red hat with the brand name for his spring 2002 couture show, and Karolína Kurková wore it for the opening. The hat circled back in 2011 when Lady Gaga wore a slasher-font version of it on Jimmy Kimmel.

Each of these chapeaux feels singular in style and essence—even though it’s the same idea simply tweaked in shape and color. “It’s the personalization that makes it feel new each time,” Treacy says. “The Valentino hat couldn’t look more Valentino, because it said Valentino. But not every word works. The word that is used is the power of it all.”

When it came to collaborating with Jonathan Anderson for his Hollywood-inspired collection presented at LACMA, it started out simple with “Dior.” “Jonathan told me Isabella was on his pin board for this show,” he says. “It’s compelling as a hat because the word is a symbol of excellence. Those four letters, they mean a lot.” Look 16—a male model wearing a glistening suit and cape, a golden Dior floating above his head—was our first look, followed by more unexpected words pulled from the works of pop artist Edward Ruscha (Star, Buzz, and Flow—perhaps a California-ified nod to Blow).

It’s been 35 years since the first Hat hat walked down the runway, and Treacy attributes their staying power to the whimsy of the design. “It looks like feathers are just floating above your head to form whatever word,” he says. “Feathers appear like the most fragile thing in nature. However, a bird has spent its life flying around the world, using its feathers to propel itself. So in fact, it’s incredibly strong and fragile at the same time. There is no material that conveys weightlessness and fragility like a feather.”