Jason Reed / Reuters

In 2017, there were 205 Ezras, 237 Lincolns, 137 Austins, and 107 Wyatts born in the U.S. who shared something unexpected in common: They’re girls.

These babies’ parents made a decision that thousands of their peers did in giving their newborn daughters a name that is generally considered male. According to Pamela Redmond Satran, who co-runs the baby-name website Nameberry, the past 10 years of government baby-naming data indicate “an overall radical increase in the number of girls getting these names.” She says that some parents “celebrate the idea of naming a baby girl James,” for instance, as an attempt to upset gender expectations by showing that girls can take on traits that are traditionally perceived as masculine.

CREDIT: The Atlantic | Data: Nameberry, social security administration

What’s noticeably absent, though, is a boomlet operating in the other direction. “It’s clear from the data that boys are not being named Sue or Sarah or Elizabeth,” Satran says. Indeed, when I looked at government data myself, I found that there was a conspicuous trend: Two of the most popular boys’ names in 2017, Noah and James, were given to 170 girls and 77 girls, respectively, that year. But the number of little boys given one of 2017’s top 10 girls’ names was as low as six and no higher than 17, which is so small that it might reflect errors in birth records. (Last year, there were estimated to be about 3.85 million births in the U.S., so even the more common practice of giving girls boys’ names is far from mainstream.)

Why aren’t there more baby boys with girls’ names? The answer has to do not just with how Americans think about gender and baby names today, but with how they’ve thought about the interplay between those two things for about a century—and with how names like Ashley, Shirley, and Shannon started off thoroughly male and ended up thoroughly female.

While parents who give their daughter a boy’s name might be trying to subvert gender norms, such a name is only desirable—connotations of “strength” and “coolness” are what Satran says some parents are after—because masculinity is seen as desirable. So it’s considered perfectly fine for a girl to exhibit traits associated with masculinity, yet a “serious problem” when men or boys reveal “even a whiff of femininity,” says Brian Powell, a sociologist at Indiana University. He says this one-way exchange is typical of scenarios in which one group of people has a higher perceived status than another; just as with the “one-drop rule,” a legal precedent that originated in the 17th century and categorized those with any “black” blood as fully black, a higher-status group avoids taking on any traits of the lower-status group.

The gender associations of a name can have a big effect on how people are perceived. A 2001 study showed that women with “androgynous” names like Casey or Kerry were perceived as more masculine than those with traditionally feminine names, while men with such gender-neutral names were perceived as less masculine. Other researchers have found that girls with gender-neutral names are more likely to take advanced math and science classes in high school and that female lawyers with unisex names are more likely to become judges.

Laura Wattenberg, the creator of the website Baby Name Wizard, remembers what happened after she listed the name Riley under the girls’ section (as well as the boys’) of her book of baby names in 2005. “I got angry letters from parents who had named their sons Riley and were furious at me for ruining their son’s name by suggesting it was legitimate to name a girl,” she says. (By then, the majority of Rileys being born were girls, as is still the case.)

As Wattenberg told me, those parents were resisting the long history of certain names making the switch from male to female. “Traditionally,” she says, “unisex names or cross-sex name usage has always been a one-way street—that is, always been boys’ names being taken up for girls. I don’t think we realize how much it happened in the past.” She’s talking about names like Ashley, Leslie, Dana, Shannon, Beverly, and Shirley, all of which started off as male names. (Ironically, the only web page I saw suggesting girls’ names for boys included multiple of these originally-male, now-female names.)

What leads some parents to pick a particular male name for a female baby over another? One factor Wattenberg mentioned is phonetics—nearly all male names ending in a vowel sound are “fair game for girls.” She also pointed to the influence of celebrities: Dakota, a “rugged, Western name,” was popular for boys in the ’90s, but underwent a rapid gender shift when the first famous Dakota (Fanning) happened to be a girl. (Long before her, Shirley Temple is credited with having given parents a similar idea about her first name.) Celebrities’ own baby-naming decisions set examples too, as Blake Lively and Ryan Reynolds named their daughter James, and Ashton Kutcher and Mila Kunis named theirs Wyatt.

Satran, of Nameberry, noted the influence of culture more broadly. Some of those Ezras, Lincolns, Austins, and Wyatts owe their names to today’s version of female empowerment, but some parents of the past have had similar thoughts. Satran cited, for instance, the “broad-shouldered power-suits trend” of the early 1980s, “when girls were first given names like Tyler or Jackson.”

Many of today’s parents of baby boys, though, do seem to be thinking differently about gender than the generation that preceded them. “Today we are seeing a quantifiable shift, that more boys are in fact being given unisex names than 30 years ago,” says Satran. She adds, “Parents might not be naming their boys Sue, but they’re naming them Robin, for instance.”

A trend in the opposite direction that Wattenberg has noticed, however, is the rise of “cartoonishly hypermasculine names like Jaxx and Ace and Titan” for boys. “There are more babies named Zeus than there ever used to be,” she says. Many parents seem comfortable giving their baby boys nontraditional names—whether unisex or über-masculine—but remain uncomfortable venturing into exclusively female territory.

Once upon a time, though, parents didn’t consider such things when deciding what to call the next generation. “Something that we don’t often realize today is that there didn’t used to be baby-name trends at all,” Wattenberg says. In the past, the inspiration for names was usually limited to one’s religion or relatives; in the early 1800s, nearly one in four girls and women in the United Kingdom were named Mary, and roughly one in five boys and men there were named John.

The late sociologist Stanley Lieberson theorized that, in the U.S., as the importance of one’s extended family and religion diminished, names were “increasingly free to be matters of taste.” Satran marks 1947 as a watershed year, when the name Linda eclipsed Mary as the most popular name for American baby girls, and after that, she says, “the balance tipped to more people choosing names because they liked them, because they were stylish or cute.” All of a sudden, parents found themselves choosing not just names, but also “deeper values or political ideals,” says Satran. From then on, a name’s gender associations became one of many criteria to be considered as parents brought their children into the world.

Which brings us to the present, and perhaps the future, of baby names. Nowadays, no name enjoys the dominance that Mary or John ever did, because so many parents seek out original names. “That means that names that had a traditional gender association are disappearing,” Wattenberg says, “and in their place are surnames [used as first names], word names, place names, just total new creations out of Scrabble tiles.”

This might seem to point to a future where names have no gendered history, and where a boy’s parents won’t be so alarmed when their son’s name gets tainted by femininity. But that’s not what Wattenberg has seen so far. “I’ve looked at what happens to those names over time, and the answer is they either disappear or they typically end up in one column or the other,” she says. In other words, gender norms will still force names to pick a side. They almost always do.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.