Amarantha is a rare botanical name whose mythical equivalent was believed to be immortal.  The Italian and Spanish form is the somewhat-more-acccessible Amaranta.

Amarantha

Blythe originated as a nickname for an upbeat person, coming from the Old English word bliðe, meaning "merry" or "cheerful." Today the homophone blithe shares the same meaning. Blythe was eventually adapted to a surname before it became a feminine given name.
 
Blythe embodies a cheerful, carefree spirit and could be the next Blair/Blaine/Blake/Brett/Britt, with the advantage that it's clearly pink. It joins other other light-hearted names for girls: Felicity, Hilary.
 Blythe is the middle name of Drew Barrymore—in her case a surname from her rich theatrical history.
 The title of the memorable Noel Coward play Blithe Spirit is taken from Shelley's poetic line, "Hail to thee, blithe Spirit"—a nice tribute to a baby Blythe.

Blythe

Columba is an early saint's name that rhumbas to a modern beat. While the original St. Columba is male, the name sounds more appropriate for a girl in the modern world. Leave variations Colm and Callum for the boys.

Columba

Delphine is a sleek, chic French name with two nature associations — the dolphin and the delphinium, a bluebell-like flower, a well as a link to the ancient city of Delphi, which the Greeks believed to be the womb of the earth. All of these derive from the Greek word delphus "womb". 
 
Delphine was very popular in France from the 1960s to the 1980s, peaking at Number 6 in 1977-78. In the US, its peak came earlier — in 1930, when it reached Number 427. Today, Delphine is absent from the Top 1000 entirely but retains its French flair, making it an even fresher alternative to stylish vintage names like Daphne and Josephine. Sophie Turner and Joe Jonas have a daughter named Delphine, which may revive the name among Americans.
 
Balzac used the name in two of his novels, and Madame de Stael wrote the 1802 epistolary Delphine, which helped bring the name into fashion in France. Delphine Seyrig was a renowned French movie actress.
 
The attractive Spanish version is Delfina.

Delphine

Eulalie hasn't ranked in the US Top 1000 since 1899, but its French roots might make it more appealing to modern ears than its sister Eulalia.
 "Eulalie" is a poem by Edgar Allan Poe, and the name also appeared in Gone With the Wind and The Music Man. It has been on the French popularity list for most of the 2000s. Eulalie Spence was a playwright from the British West Indies who contributed to the Harlem Renaissance.

Eulalie

Frederica is an interesting possibility for the parent unintimidated by its old-fashioned formality, and who can appreciate the
vintage charm and verve lurking inside its stuffiness. 
 The name emerged in eighteenth century Prussia when supporters of King Frederick the Great began to name their daughters in his honor, and is currently reporesented by opera star Frederica von Stade.
 Nicknames include the obvious Freddie, plus Rica and Fritzi.

Frederica

Gwendolen, an ancient Welsh favorite, retired decades ago in favor of the short form Gwen, but now, as in the case all across the naming board, the nickname has faded and the more distinguished original is up for reappraisal. Gwendolen means "white circle," probably alluding to an ancient moon goddess, and appears in both Welsh and English legend, once as a fairy with whom King Arthur fell in love and another was the wife of the wizard Merlin.
 Gwendolen is the name of principal characters in George Eliot's novel Daniel Deronda and in the Oscar Wilde play, The Importance of Being Earnest.
 An alternate spelling is Gwendolyn, as in Gwendolyn Brooks, the first African-American woman to win a Pulitzer prize for poetry. Gwendolyn, always the more popular spelling in the U.S. and the full name of the character Winnie Cooper on The Wonder Years is now at Number 514, having reached as high as 112 in the 1950's.
 Singer Gwen Stefani was actually christened Gwen.

Gwendolen

Despite the possibility of gender confusion, the Hero in Greek myth was a woman. Myleene Klass got that when she chose Hero for her daughter, and Sam Taylor-Wood and Aaron Johnson used it as their daughter's middle--and we wouldn't be surprised to see more girls with this heroic name.
 In Greek legend young Leander swam across dangerous waters every night to court his beloved Hero. In Shakespeare's Much Ado About Nothing, Hero is the love interest of Claudio and cousin of Beatrice.

Hero

Imogene

Jonquil is an unusual flower name that is less outlandish than Daffodil and less common than Daisy. It just might appeal to parents seeking a singular botanical option. 
Unlike most flower names, Jonquil wasn't introduced until the 1940s, and saw some usage in the U.K. during the forties and fifties.

Jonquil

One of the most adaptable of the Middle Eastern names, partly because of its similarity to the western Camilla. 

Kamilah

Louise has for several decades now been seen as competent, studious, and efficient—desirable if not dramatic qualities. But now along with a raft of other L names, as well as cousin Eloise, Louise is up for reappreciation—sleek and chic, stylish in Paris, and starting to become so in the US as well. Louisa is perhaps more in tune with the times, but Louise has more edge. Louise has been on the rise lately, and reentered the US Top 1000 for the first time in a quarter century in 2016.
Louise has been a royal name in several countries, including Denmark, Sweden, France and England: currently Queen Elizabeth has a granddaughter named Louise via her son Prince Edward. It has been a staple on the Top 10 lists in Belgium and France in recent years.
Among her most notable bearers: iconic film actress Louise Brooks and modern sculptors Louise Bourgeois and Louise Nevelson. Louise is the middle name of both Madonna and Meryl Streep, and Louise was the character played by Susan Sarandon in the feminist road movie Thelma and Louise.
And there's also a nature reference—the beautiful Lake Louise in the Canadian Rockies. Louise is one of many classic names newly fashionable as one of the trendy <a href="https://nameberry.com/search/girls-names/l">girls' names starting with L</a>.

Louise

If you're looking for a fresher belle name than Isabelle, Mirabelle is lovely, and we also like the extra flourish of Mirabella. And if you want a nature tie, Mirabelle is also the name of a delicate French plum.
 Steve Martin chose the name for the heroine of his novel Shopgirl, Mirabelle Buttersfield. And the Mirabel spelling was used for the likeable heroine of the Disney animation Encanto.

Mirabelle

Niamh, derived from the Old Irish Niam, is an ancient Irish name that was originally a term for a goddess. In Irish myth, one who bore it was Niamh of the Golden Hair, daughter of the sea god, who falls in love with Finn's son Oisin and takes him to the Land of Promise, where they stayed for three hundred years. Niamh can be Anglicized as Neve, Nieve, or Neave.

Niamh is particularly popular choice in Northern Ireland, Ireland, Scotland and England and Wales. Niamh Cusack is part of the acting family that also includes Sinead (wife of Jeremy Irons), Sorcha and Padraig. Americans have recently become better acquainted with Niamh via the heroine of Christina Baker Kline's bestselling novel Orphan Train.
Here, the Anglicized Neve would undoubtedly prove simpler, if less intriguing. Actress Neve Campbell pronounces her name (a family name) "NEV", and Neve is the daughter of Conan O'Brien.

Niamh

Ophelia reentered the US Top 1000 in 2015 after more than 50 years off the charts, and rose more than 600 spots since then, with no signs of slowing down. Could Ophelia may be the next Olivia?
 Ophelia is a beautiful name that has long been hampered by the stigma of Hamlet's tragic heroine—for whom Shakespeare seems to have invented the name—but more and more parents are beginning to put that association aside. There is also a gutsy Ophelia in Harriet Beecher Stowe's 1852 Uncle Tom's Cabin, which seems to have had some influence on baby namers at the time.
 
 Among the actresses who have played modern non-Shakespearean Ophelias are Jamie Lee Curtis and Blake Lively. The heroine of the film Pan's Labyrinth used the Spanish spelling, Ofelia.
 Actress Patricia Neal and author Roald Dahl named one of their now grown daughters Ophelia, and more recently musician Dave Grohl named his baby girl Ophelia Saint.

Ophelia

Pearl, like Ruby, has begun to be polished up for a new generation of fashionable children after a century of jewelry box storage. The birthstone for the month of June, Pearl could also make a fresher middle name alternative to the overused Rose. Cool couple Maya Rudolph and Paul Thomas Anderson named their daughter Pearl Minnie, followed by Jack Osbourne, and several celebs have put it in the middle spot, as in Busy Philipps's Cricket Pearl, Jake Owen's Olive Pearl and Caleb Followill's Dixie Pearl .
After being a Top 25 name in the late nineteenth century, Pearl went into a long slide, but is showing signs of a strong comeback -- it reentered the Top 1000 in 2010.
 In Nathaniel Hawthorne's The Scarlet Letter, Pearl is the illegitimate daughter of Hester Prynne, who gives her the name because she is 'her mother's only treasure.'
 Pearl was also the alter ego name of Janis Joplin, tied to singer Pearl Bailey, and---hmm--the birth name of western writer Zane Gray.
 Variations are PERLE and PERLA.

Pearl

Quirina is the feminine form of Quirinus, the name of the Sabine god of war. This is one mythological name that has not traveled to the modern world -- we've found no babies ever name Quirina or Quirinus in the US -- but with this newly-trendy class of names, anything is possible. 

Quirina

Most of us had never heard this lovely Welsh name with links to the moon until we heard the 1976 smash hit Fleetwood Mac song of that name, with lyrics by Stevie Nicks. That same year it popped onto the U.S. Top 1000 at Number 593. 
 After giving his four boys extreme rebel names, director Robert Rodriguez bestowed this sweet name on his first daughter.
 According to Celtic legend, Rhiannon's birds sang more sweetly than any others; she herself was known for being forthright and witty.
 Rihanna looks similar but is unrelated.

Rhiannon

Seraphine is the Gallic version of the angelic name Seraphina. But while Seraphina has been rising rapidly since Jennifer Garner and Ben Affleck chose it for their second daughter, Seraphine has been largely ignored, though we believe the French vowel-sound ending will soon be more stylish than the a-endings that have predominated in <a href="https://nameberry.com/girls-names">girls' names</a> for years.

 Another cousin, Seraphita, is the heroine of an eponymous 1837 Balzac novel.

Seraphine

Talullah or Talulla, the old Irish name of two early saints, is almost identical to the Native-American Tallulah. A modern hipster favorite, however it's spelled.

Talullah

In an epic poem, the personification of truth, beauty, and unity; this ancient name is popular in several European countries but less common in the US. The Oona spelling is slightly more popular but Una sleeker.

The name of a heavenly planet and the Roman goddess of beauty and love was an intimidating no-no until tennis champ Venus Williams put an athletic, modern spin on it. 
 
Associated with the Greek Aphrodite, in the Roman pantheon, Venus (whose name probably means "desire") was considered the mother of the Roman people and has always been a favorite subject of artists — most well-known being the prehistoric sculpture Venus of Willendorf, the ancient Venus de Milo and Botticelli's The Birth of Venus.

Venus

Wilhelmina was long burdened with the Old Dutch cleanser image of thick blond braids and clunky wooden clogs, but that started to be changed somewhat by the dynamic Vanessa Williams character on Ugly Betty, and even further by the choice of Wilhelmina by ace baby namers Natalie and Taylor Hanson. For the less adventurous, Willa is, for now, still a more user-friendly female equivalent of William.
 Wilhelmina was a lot more commonly heard in the U.S. at one time: it was as high as Number 215 in the 1880s, but has been off the list completely since 1955.
 Queen Wilhelmina reigned in the Netherlands for most of the early twentieth century, becoming a heroic figure during the two World Wars. The name got an infusion of glamour via Wilhelmina Cooper, the Dutch-born model who established the top Wilhelmina Model Agency in 1967. Wilhelmina "Willie" Scott was the name of the Kate Capshaw character in Indiana Jones and the Temple of Doom.
 To enliven her image, Wilhelmina has a plethora of nicknames: Mina, Minna, Minnie, Billie, and Willa. Wilma.

Wilhelmina

The name of a Christian saint and a city in Ohio, Xenia is one of the more accessible and intriguing x names. It is the name of one of the Bond Girls--played by Famke Janssen in the film "GoldenEye."

Xenia

This French name has the elegance of other '-ette' names such as Colette and is a botanical name without being too obvious about it. 

Yvette

With historical roots as a beautiful and intelligent ancient queen and literary ties to Hawthorne and Edith Wharton novels, this rarity could appeal to adventurous parents seeking the romantically unusual. Tina Fey used it as her daughter Alice's middle name.
 Zenobia was the intriguing third-century Queen of Palmyra who for a time ruled the eastern Roman Empire, Ethan Frome's wife Zeena was born Zenobia, and Zenobia Moodie was one of the most colorful characters in Nathaniel Hawthorne's The Blithedale Romance.
 Zenobia reached a high of Number 683 in 1909 but had dropped back out of the Top 1000 by the mid-1920s.

Zenobia

anonymousthinker's list "anon's ABC - Girls" of 26 great name ideas: Amarantha - Zenobia!