Better strictly as nicknames

Jace may sound like only half a name -- it's usually pronounced like the first half of Jason though some may consider it a spelling-out of the initials J. C. -- but it's a popular choice for baby boys. Jace has been heard on such TV shows as Teen Mom 2 and Duck Dynasty.

Jack may have fallen from its Number 1 place in England, but in the US it's as popular as it was at its height in the 1920s and 1930s. A durable, cheery, everyman form of John, Jack ranks as one of the most popular boy names starting with J.

Jackie Kennedy gave this name a lot of style, but it doesn't seem destined for a comeback the way brother name Jack has. Jackie and Jacqueline both peaked in 1961.

Jackson is one of those names that's much more popular than you think, coming in near the top of our annual Playground Analysis, which ranks names by grouping all their spellings together. There were nearly 17,000 baby boys named Jackson -- along Jaxon, Jaxson, Jaxxon, Jaxen, Jaxyn, Jaxsen, and Jaxsyn -- which counted together makes it the Number 3 boys' name.

Jamie is typical of the relaxed unisex names starting with J that seemed so cool in the sixties after decades of Jeans and Joans, though now pretty tepid. Jaime and even Jamey and Jayme are alternate spellings.

The cool form of James in the 1970s and '80s for both sexes. Still a more stylish short form than Jimmy, though many parents will want to call James by his entire, not-very-long name.

Very Brady Bunch.

Jessie has never been used as much as Jennie/Jenny, partly because it's a boys’ name as well (spelled Jesse), but it does have a friendly and unpretentious pioneer feel. In Scotland, it's found as an Anglicized form of Teasagh, itself a form of Jean, and is used as a full name. And in the rest of the world, Jessie may be short for Jessica or used on its own.

Josie is jaunty and friendly: among the most winning of all nickname names. She's been on the social security list since records began being kept.

Kai is an internationally flexible name with many possible origins and meanings, growing in popularity in the US and a diverse range of European countries.

Kate, in the headlines via Catherine Middleton aka the Princess of Wales, has been as pervasive as Kathy was in the 1950s and 1960s, both as a nickname for Katherine and Kaitlyn and as a strong, classic stand-alone name.

Friendly mega-popular short form of Katherine that has definitively replaced Kathy, Katie is often given on its own. Going forward, though, Katie is more stylishly clipped itself to the grownup Kate.

Kia is a sweet, simple name that is now, unfortunately, associated with a Korean car label. Better today: Nia, Thea, or Keira.

Kristy (and Kristi and Kristie) are the ultimate kool girl nicknames of the sixties and seventies, not kwite as kute any more.

This body of water runs deep; the best of a group of new possibilities that includes Bay, Ocean, River, and the more established Brook. It has received attention via the actress Lake Bell. Lake would make a particularly cool and refreshing middle name, as Gisele Bundchen and Tom Brady did for daughter Vivian.

The original brief, breezy name is somewhat out of favor now even as a middle name. The Leigh spelling has more substance and is more identifiable as female.

A name that has a bit of a shouldn't-I-be-a-middle-name sound, though still in use as a first for both genders. Lee might be a good choice if you want something that sounds at once traditional yet modern, unisex but not newly-minted.

This spelling variation of Leya was popularized by the Star Wars films, but is still firmly in the US Top 1000 many years later. This spelling is also probably preferred as it is clearer in pronunciation to the original Hindi name, Leya (which sometime gets pronounced Lee-ah).