We all know about the once-male names like Madison and Addison, Harper and Alexis that have become popular girls’ names.

Then there are the newer names crossing the gender divide toward the girls’ side. These may still be more widely used for boys, but have now moved into the Top 1000 for girls: Sawyer, Hunter, Ryan, Dallas, Ellis and August — the name Mark Zuckerberg and Priscilla Chan recently gave their second daughter — are the most notable.

More obscure than these, but way more newsworthy, are the boys’ names that don't make the Top 1000 but are being used for sizable numbers of girls.

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We don’t mean word names like Rebel and Timber that are not intrinsically gendered, or nicknames such as Billie and Joey that have long been used for girls, or even established unisex names such as Rowan or Robin. We’re talking about deeply traditional boys’ names that are being used, in many cases, for literally hundreds of baby girls.

In a few cases, there are powerful celebrity influences nudging these boys' names girlward, such as Blake Lively and Ryan Reynolds naming their first daughter James or Mila Kunis and Ashton Kutcher naming their little girl Wyatt. We've starred the names that are being used more often for girls thanks to a celebrity.

Most fascinating are those gender-shifting names that have been traditionally used for boys since Biblical or Roman times … or at least since 1880 in the U.S. Some names in this group may be international choices that have not be widely used in the U.S. until recently for either gender, but that are conventional male choices in their native cultures. These classically male names, with the number of girls who were given them in the US in 2015, include:

August, 242

Spencer, 237*

Ezra, 205

Tyler, 202

Carson, 177

Lincoln, 157*

Austin, 151

Noah, 137

Jude, 135*

Christian, 124

Hudson, 114

Evan, 97*

Ira, 97

Mason, 91

Asher, 74

Anderson, 74

Sullivan, 70

Gianni, 69

Jules, 66

Asa, 65

Wyatt, 63*

Aiden, 60

Hanan, 60

Kyle, 60

Lamar, 60

Levi, 58

Everett, 44

Wesley, 43

Jasper, 42

Maxwell, 40*

James, 38*

Michael, 36

Reed, 36

Soren, 34

Landon, 32

Atlas, 30

Judah, 30

Uriah, 28

Finn, 26

Brady, 35

Julian, 26

Sonny, 26

Barrett, 25

Killian, 25

Roman, 25

Blaise, 24

Davis, 24

Jackson, 24

Jonah, 24

Alexander, 22

Connor, 21

Declan, 21

Liam, 21

Oliver, 20

Sebastian, 20

The next group are names that have become widely used for boys only over recent decades. You might argue that these newer names are less tied to any one gender. This list includes some traditional last names, mainly because it’s too difficult at this point to know whether to call names such as Chandler and Grayson surnames or names.

Chandler, 248

Campbell, 224

Baylor, 215

Ashton, 189

Bentley, 183

Palmer, 176

Grayson, 168

Raleigh, 154

Ryder, 133

Channing, 118

Cooper, 110

Lane, 97

Kyler, 94

Maddox, 90

Ramsey, 83

Jensen, 75

Miller, 71

Grey, 70

Paxton, 69

Tanner, 68

Dawson, 66

Auden, 62

Chase, 62

Chevy, 62

Jameson, 53

Ryker, 49

Beau, 44

Bowie, 41

Dempsey, 35

Windsor, 32

Rivers, 31

Tate, 31

Hayes, 26

If you go below 20, you find lots of boys’ names given to a handful of girls: There were reportedly 18 baby girls named David in 2015, along with nine named Henry and five named Maximus and Oscar. But to give you an idea of how rare that is, there were the same number of baby girls named Maleficent and Ziyi.

So what does this mean, in the larger sense? We don't foresee Ezra and James becoming the Addison and Madison of the future, or even advocate that parents of girls rush over to the boys' list to find fresh and edgy names for their daughters. But the growing numbers behind this phenomenon are evidence that gender is becoming as fluid a concept with names as it is in other areas of life, and that's a development we wholeheartedly support. But it will take parents naming their sons Sarah and Serena for us to achieve true gender parity.