Gender Benders

Once the quintessential bouncy teenager name, Kelly helped launch the trend of unisex Irish names . But it now takes a backseat to more substantial surname names like Kennedy.

Kendall, as used for a girl, was initially propelled by a soap opera character (Sarah Michelle Gellar as Kendall Hart in All My Children) and reality star and Kardashian sister Kendall Jenner.

Unisex name around for several decades for boys and now ripe for girls.

Knox is an old Scottish surname that Brad Pitt (whose great-great-grandfather was named Hal Knox Hillhouse) and Angelina Jolie took out of the back cupboard, dusted off, and elevated to coolness--to the point where it entered the popular baby names list in 2009. Knox now ranks among the most influential celebrity baby names.

Lennox is one of the new breed of surname names on the rise as a Scottish name for girls as well as boys. The final x makes the name a bit masculine a la Max and Felix, but female inspirations include Eurythmics' Annie Lennox, Mary Lennox in The Secret Garden, and Lennox Scanlon in sitcom Melissa & Joey.

Lex is still used mostly for boys, but like Alex, may cross over with the rising popularity of all long forms of the name. Lexi is another, more feminine option.

Logan, with its appealing Scottish burr, is a very hot boys' name—it's in the national Top 10 and heading for Number 1 in some states—and can also make a rich and resonant choice for a girl. Jason and Jordan Mewes have a daughter named Logan Lee.

Magnus is a Latin name, literally meaning "greatest," that has a Scandinavian feel. It dates back to Charlemagne being called Carolus Magnus, or Charles the Great. Norwegian king Magnus I, named after Charlemagne, introduced it to his culture, and thus Magnus was the name of six early kings of Norway and four of Sweden. It is still a highly popular name in Denmark and Norway.

If Sam can make it as a girl's name, why not Max? Facebook founder Mark Zuckerberg's eldest daughter Maxima goes by Max, but you could also use it as a short form for Maxine, Maximilienne or even Margaux.

Not one but two Spice Girls are named Mel, which led to it briefly being more popular for girls than boys in the 90s and early 00s, but it has now fallen out of favor for both sexes.

Briefly cool in the 1950s, but now gone the way of Ricki and Nikki. More contemporary: Mikie or Mikey.

Milo is most commonly considered to be Germanic name derived from the Latin word miles, meaning "soldier." However, there is evidence to suggest it also may have independently spawned from the Slavic root milu, meaning "merciful." Milo predates brother name Miles, a variation that evolved when the name immigrated to the British Isles in the Middle Ages. Mylo is an alternate spelling.

Oakley, with its nature name roots and its Annie Oakley charm, is a hot name for both genders but more than twice as popular for girls. This name made it into the Top 1000 for the first time in 2013, one of only four girl names starting with O to rank that high. A decade letter, it's aiming for the Top 100.

Rarely used until the 90s, Payton rose up the charts when it was popularized by the football star, Peyton Manning, and, interestingly, by the character of "Peyton Flanders", the villainess of the 1992 film, The Hand That Rocks The Cradle.