Callum is a gentle, charming name of Scottish origin, that is a popular choice across the UK. In the US, it was a rare option until the late 2000s, however, since 2017 it's been rising up the ranks. Complete with easy, breezy and cool nickname Cal, it climbed more than 60 places in the US in 2024, placing it just outside the Top 150.

One of the most romantic of appellations, Caspian is a geographical name referring to the large salty sea between Asia and Europe. It's also the name of the hero of C.S. Lewis's beloved Chronicles of Narnia, Prince Caspian.

Rugged but gentle at the same time, Cassian is a saintly and stylish choice that was derived from the name Cassius. Before 2017, it was an obscure choice, given to a tiny handful of boys each year. As of 2023, however, it's become one of the top ten fastest-rising names in the US, more than doubling in usage since 2022 and edging closer towards the Top 500.

Cyrus is one of those surprising names that have always ranked among the Top 1000 boy names in the US. On an upward trend since the mid-90s, Cyrus now sits in that comfortable place between too popular and too unusual.

This no-nonsense German variation of Charles is strong and sturdy. A top choice throughout the 20th century, Carl is now verging on falling off the charts.

Caleb is an attractive Old Testament name that has been in the US Top 100 for nearly three decades now. Consistently popular but never too popular, Caleb feels more like a classic than a momentary trend.

This ancient name, also spelled Caspar, is finally shedding its ghostly image and moving into the 21st century. Popular in the Netherlands and Scandinavia, where it's sometimes shortened to Cas, Casper could ride the style coattails of cousin Jasper.

Solid and intellectual, with just a touch of ruggedness thanks to that rad ending, Conrad has appeared consistently in on the US popularity charts since the 19th century. Over the years, it has been leant a literary air by the writer Joseph Conrad, a pop of rock energy by the Elvis-like character in the movie Bye, Bye, Birdie, and more recently, a serious, kind-hearted, and handsome feel by The Summer I Turned Pretty.

With its friendly, sensitive, and approachable feel, Cameron is a 90’s favorite that remains popular today. It has a pleasing balance of soft and strong sounds, and holds unisex appeal, thanks to Cameron Diaz. Still, eight times more boys than girls are named Cameron in the US.

Charlie derives, of course, from the classic name Charles which, in turn, comes from a German word meaning "free man." Charles became very popular in France during the Middle Ages due to the fame of Charles the Great, also known as Charlemagne. Charley is an alternate spelling.

Cassius, a Shakespearean name rooted in antiquity, is trending in a major way. It's one of a raft of Cas-starting names for both boys and girls, including Caspian, Cassian, and Cassia, that are enjoying a new moiment in the sun.

Charles derives from the Germanic name Karl, meaning "man" or "free man", and is a royal name in multiple European countries. A famous early bearer is Charlemagne, King of the Franks and Lombards and then Roman Emperor in the 8th-9th centuries.

Cillian is one of the native Irish names that, along with Aiden and Declan, is becoming an unlikely favorite in contemporary America. The Killian spelling has been more popular in the US, but Cillian's star is rising, perhaps thanks to Irish actor Cillian Murphy, star of Oppenheimer and Peaky Blinders.

Calvin is a slightly quirky but cozy name that has a fashion edge thanks to Calvin Klein. It has been steadily on the popularity list since records were kept, never lower than Number 250, peaking in the 1920s, the era of the Calvin (originally John Calvin ) Coolidge presidency.

The genial yet upscale and preppy Cooper was one of the first occupational last names to catch on -- and Cooper remains a pleasing option.

With a touch of celestial power, a hint of clunky charm, and the totally cool -o ending, Cosmo may well be finally shaking itself free of both the Seinfeld association (which made it a punchline of a joke) and the cartoon fairy association from The Fairly OddParents. In fact, it is in the Top 1000 in the UK and a favorite on Nameberry.

Cole -- a short name that embodies a lot of richness and depth -- has long been associated with the great songwriter Cole Porter. It's quite popular in Scotland.

Even though in the past Clyde may have been identified as half of the infamous outlaw duo with partner Bonnie Parker—especially after the 1967 movie in which he was played by Warren Beatty—Clyde has always had an element of jazzy cool that could overcome all the rest.

This anglicized form of the Irish surname Ó Cathaláin links back to the Irish given name, Cathal. Similar to Callum, Caleb, and Calvin, it might feel more usable outside of Ireland and Scotland than its origin name.

Crusoe, as in castaway hero Robinson, is a literary invention by author Daniel Defoe. In the novel, the character says his name is an Anglicization of the German Kreutznaer, which may be a place name or refer to a crossing of the river Nahe. Alternatively, it may translate to "dweller by the cross", from Kreuzbewohner.