(CBS News) Katherine Hepburn, Jean Seberg and Jane Birkin all have that unidentifiable sort of je ne sais quoi.
Well now, writer Lizzie Garrett Mettler has categorized that certain something as "Tomboy Style."
The freelance writer transformed her popular blog that chronicles the history and fashion of the tomboy into a book, published by Rizzoli, due out April 3.
"I remember at one point realizing there was a shift in the word tomboy," Mettler told CBSNews.com. "Growing up, I was completely a tomboy, but then when I became a teenager I shied away from that word, because I sort of thought of it as a pejorative. I didn't see it as a word that necessarily spoke as something that was uber-stylish, trendy or cool."
Though, later in life while perusing fashion blogs she saw the word come back up again - this time with a whole new connotation.
"I kept hearing these bloggers say, 'Oh I love this girl (we'll say it was a Sartorialist photo or something) she's so tomboy chic, or she's got great tomboy style.' And I was kind of like, 'Huh? That's a thing now?' Then the wheels started turning and I thought 'What makes a tomboy stylish?'" Mettler explained.
It was from those questions that she decided to start a blog in May 2010 to serve as her "inspiration board." The self-proclaimed history and 20th century pop-culture obsessive said the blog was a way to tie in love for both history and fashion.
"It is a lot about fashion, but it's a lot about what these women were saying and doing. And what was the era and context of this fashion," said Mettler.
While turning the blog into a book wasn't the plan all along, Mettler says she thought "very early on" that the subject matter would make a good book, but logistically wasn't quite sure how to get that done. Eventually, her proposal landed on someone's desk at Rizzoli and roughly six months later she had a book.
The book looks at seven different types of tomboys: the rebel, the sophisticate, the jock, the prep, the adventuress, the girl next door and the naturalist.
While Mettler currently channels her style icon Jane Birkin and the "preppy -girl -next -door" type - wearing lots of white denim and colored jeans with striped boat-neck T-shirts - that wasn't always the case.
"I wore boys' clothing, strictly boys clothing, for probably five years of my childhood," said Mettler. "And this was the '80s and early '90s, so it was sweatpants and... Well we lived in California for a while so it was surf clothes, Quiksilver shorts, and striped shirts with rolled-up sleeves - all neon. Anything my older brother was wearing I would basically get in a year or two and wear, even though it didn't fit."
Now, if Mettler had her pick, she would dress in all Rag & Bone, A.P.C. or The Row, with looks inspired by Birkin or her daughter, Charlotte Gainsbourg, whom Mettler admits she has an "out-of-control girl crush on."
"Jane Birkin is the whole package. When she was in her 20s, 30s and 40s, she had messy hair, [she wore] T-shirts and jeans she just put them on that day and didn't even think about it."
But, to Mettler "Tomboy Style" isn't just about the clothes.
"It's the clothing that would identify a woman as a tomboy perhaps initially, but it is really about the spirit underneath the clothes that makes her. I think there is something inherent about her and it's confidence, rebelliousness and a sense of adventure that kind of almost grasp all of it," explained Mettler.
As far as writing more books, Mettler is still undecided. She has another proposal idea, but worries that "Tomboy Style" would be hard to follow up.
"'Tomboy Style' has definitely been a passion project," she said. "[It has been] One of the most inspiring and greatest creative projects I think I'll probably maybe ever work on."