Refers, in literal terms, to a curved line -- as in Martin Luther King, Jr.'s famed "arc of justice." Could also be used as a reference to Joan of Arc -- Arc being, there, derived from her father's name, rather than a place -- or, conceivably, to Noah's Ark.

Arin

Beau suggests someone devilishly handsome, with a large measure of southern charm—a nice image to bestow on your boy. Often solely a nickname in the past, it's now standing firmly on its own. Beau has been on the Social Security list non-stop since 1969.
 Beau also has something of a dapper image, thanks to the fashionable Beau Brummell (born George), which led to the stylish New York mayor Jimmy Walker being called Beau James. Other notable Beaus had more formal names at birth—Beaus Bridges and Biden were both the third sons in their families to carry their fathers' names: Lloyd Vernet Bridges III and Joseph Robinette Biden III.
 P.C. Wren's novel Beau Geste was a major bestseller in its day and was also a popular movie—in that case Michael was the character's birth name. Many will remember that the child of Ashley and Melanie Wilkes in Gone With the Wind was called Beau, and there was also a Beau on the old TV western Maverick.
 And if you want a more substantial name on the birth certificate, try Beauregard.
 Art Garfunkel, Emma Bunton, Wendy Wilson, Jamie-Lynn Sigler, and now Tori Spelling all have sons named Beau.

Beau

The simple and attractive Bryn is well used for boys in Wales, and does have a history as a male name in the US, although both Bryn and Brynn are currently far more popular for girls.

 Fans of British TV sitcom Gavin and Stacey will recognize it as the name of Stacey's lovable and eccentric uncle, played by Rob Brydon.

Bryn

A homey sitting-by-the fire-type nickname name. 

Laid-back and humble, with a distinctive down-home charm. 

Clem

Egen

As a name for boys, Esra is usually considered a spelling variation of the Biblical Ezra. Esra has a separate life as a Turkish girls' name.

Esra

In English, a fen is a wetland fed by surface and/or groundwater. In Dutch and Frisian, it's a traditional diminutive of names containing the element frid, meaning "peace". Either way, Fen makes a fresh alternative to fashionable Finn.

Great middle name choice for music lovers or those with Scottish roots, also spelled Fyfe.

Fife

Finn is a name with enormous energy and charm, that of the greatest hero of Irish mythology, Finn MacCool (aka Fionn mac Cuumhaill), an intrepid warrior with mystical supernatural powers, noted as well for his wisdom and generosity. 
 Finn was chosen by cool couple Christy Turlington and Ed Burns for their son, and also by Jane Leeves and Autumn Reeser. Played by Cory Monteith prior to his death, Finn Hudson was a prominent character on Glee.
Other up-and-comers in the same family: Finlay and Finley, Finian and Finnian, Finnegan and Finnigan, and, from Germany, Fynn.

Finn

Fox is one animal name backed by a longish tradition, and then popularized via the lead character Fox Mulder on X Files. Fox is simple, sleek, and a little bit wild, and could make an interesting middle name.
 It was reported that the TV character's first name was not a tribute to the Fox network which aired The X-Files, as often assumed; show creator Chris Carter said he had a childhood friend named Fox. Fox was one of the fastest-rising boys' names of 2016, perhaps because of the popularity of the X-Files revival.

Fawn

Pronounced zheel, it's a dashing conquistador; as gill, it's the nice and slightly boring guy down the street. 

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.
 
In the US, the name Kai is most commonly referred to as being of Hawaiian derivation, meaning "sea." In Europe, Kai is largely considered to have Frisian origin as a diminutive of the name Kaimbe, meaning "warrior", or as a short form of Gerard "brave spear". 
 
Kai is also found as an independent name in African, Chinese, Turkish and Native American cultures. Kai is a strong, evocative multi-cultural name that packs a lot of power in its single syllable. 
 
Famous as the name of the boy enchanted by the fairy-tale Snow Queen, Kai was chosen for her son by actress Jennifer Connelly and as a middle name for son Samuel by Naomi Watts and Liev Schreiber. 
 
Kai is popular with Berries as both a first and middle name choice. Perhaps because of its international familiarity, Kai is popular in video games. Its most prominent namesake is Danish-born jazz trombonist Kai Winding.
 
Kai ranks in the US Top 1000 for girls, but is used more than 90 percent of the time for boys. Donald Trump, Jr. has a daughter named Kai Madison and Gigi Hadid and Zayn Malik named their daughter Khai in 2020.

Actor Kit Harington, aka the dreamy Jon Snow on Game of Thrones, has given this nickname-name new style and appeal for boys. Actress Jodie Foster used it for her son. 
Kit is one of those names that is gender-neutral but has a different derivation for boys and girls. For boys, it originated as a short form of Christopher, while for girls, it's an updated diminutive of Katherine.
Kit as a full name is still beneath the Top 1000 for both sexes in the US, but it's getting more popular. In 2022, 166 baby girls and 137 baby boys were named Kit, up from 104 and 129 in 2021.

With the rising popularity of Kai, this more phonetic spelling has been gaining traction as well. Kye debuted in the US Top 1000 in 2015, and was one of the fastest-rising names of the year in 2016.

Cool short form of Alexander, fresher than Alex and less trendy than Xander... for now.

Luka is one of the coolest names in recent years, following suit of its cousin Luca which is now a Top 50 name. Luka is on its way up the charts and may crack the Top 100 in the very near future. 

Luka has a lot going for it — it is following the tails of Lucas and Luke which have been enjoying significant popularity for years. It also boasts the very current "-ah" ending sound that feels fresher than ever for boy names, from Noah to Ezra to Judah. The "k" in the middle gives an extra edge as well.

Luka

Okay, this is going to be confusing...

 There is a female figure in the Old Testament named Noa or Noah, whose name derives from the Hebrew No'ah, meaning "motion". The popular Biblical male name Noah (sometimes spelled as the streamlined Noa) is derived from a different Hebrew name: Noach "rest, repose" – although confusingly they are often written the same in English. 

 Noa is the modern Hebrew spelling of the female name, and is very popular for girls in Israel, as well as in several European countries, including Spain, Portugal, and the Netherlands. But Noa is also a popular spelling of the male name Noah in countries including France, Croatia and Bosnia and Herzegovina.

 So is a boy named Noa named after a female Biblical figure (whose name means "motion") or a male one (meaning "rest")? That's up to you! The ideal of gender neutrality means nothing belongs exclusively to one sex or the other, and that includes the spellings of Noa/Noah.

Noah is nearly a patriarch of popular baby names at this point, going from Old Testament graybeard to Top 10 name in 2009, hitting Number 1 in 2013, and now settled into second place in the US for five years. 

Noah was derived from the Hebrew name Noach, which itself came from the root nuach, meaning "rest." In the bible, Noah was deemed the only righteous man of his time, singled out by God to survive the great flood sent to punish the world. He built his famous ark, onto which he herded a pair of every animal.
 
A generation or two ago, Noah seemed far too antiquated to become a popular name. But now, along with brethren Abraham, Moses, and even Elijah, it's eminently baby-worthy. 
 
Noah's popularity is widely international, ranking highly in all English-speaking countries along with France, Germany, Italy and Spain. Noah is also a top name in countries as diverse as Belgium and Brazil, Norway and Chile.
 
Actor Rupert Graves and singer Michael Buble both have sons named Noah. Billy Ray Cyrus, responsible for the name Miley, crossed gender lines to call another of his daughters Noah. 
 
The feminine homonym Noa -- which isn't a form of the Biblical male Noah (it's a separate female name from the Old Testament) -- is currently the most popular girls' name in Israel. And Noah itself, with its vowel ending, is evidence of the trend toward softer sounds in boys' names, along with brothers Joshua and Asher.
While variation Noa is an actual girls' name drawn from a female figure in the Bible, it is sometimes used as a sleekened spelling of Noah.

Noah

Attractive, simple Japanese choice that, while not strictly unisex, could work even better for a girl, especially now that Kim Kardashian and Kanye West use it as the nickname for their daughter North. Nori is also the name of an edible seaweed used in wrapping sushi.
 
Nori also has roots as an Old Norse name, either a derivative of Nórr, meaning "north," or the word nori, referring to a small person.

Nori

Warm-hued spelling spin on Rowan that was chosen by Sharon Stone for one of her three young sons.

Roan

Rody

Rynn

Riya

A smart and simple unisex Japanese name meaning "sky". It actually has a second nature meaning in Finnish, albeit a slightly less appealing one: "gravel".

Sora

Despite its rakish western charm, still remains a cowboy costume without a real persona inside. 

Tizi

halcyin's list "Gender Neutral 3 and 4 Lettered Names" of 34 great name ideas: Arc - Tizi!

Gender Neutral 3 and 4 Lettered Names

Names that are 3 or 4 letters. Geared towards names that feel more gender neutral, or can be used for any gender. Also names that are usually more uncommon/have heard less of in use.