Appoline

Admiranda

Aelfleda

Aeluin

Aelyth

Aethelinda

Almarick

Amiria

Amphelisia

Ansfrid

Assurance 

Atilda

Avicia

Ayfara

Britannia

Bithiah

Blavier

Bonaventure

Brilliana

Celestria

Chrysogon

Clariandra

Clarimund

Cressin

Dunestan

Easter has been used as a name for several hundred years, as part of the day-naming tradition; now, this rarely heard holiday celebration name would make a novel choice for a springtime baby. 
Background:The early Anglo-Saxon monk and scholar Bede took the name of a goddess--Eostre-- whose feast was celebrated at the vernal equinox and gave it to the Christian festival of the resurrection of Christ.
 Easter appeared on the Top 1000 list during the first few decades of the twentieth century. It was heard for the character played by Jasmine Guy in the TV miniseries Queen.
 International versions include Pascal, Pasqua and Pascua.

Easter

An older form of Everett that stays closer to its Germanic roots. Distinguished Everard is the name of several historical figures and literary characters, including a minor hobbit in The Lord of the Rings. Yet, even now that Ever- names are the height of style, Everard hasn't been seen on the charts for decades.

Everard

Eglentyne

Emeria

Emmony

Emont

Estrelda

Fenwick

Ferand

Galiena

This name of the courteous Knight of the Round Table, the nephew of King Arthur, has long been superseded by its Scottish form, Gavin. 

Gawain

Gidon

Gunnor

Gwenllian

Hemon

Hesdin

Idonea

Jamys

Jonothas

Laurencia

Lefwenna

Leofrick

Loveday

Mariabella

Maynilda

Merewen

Odierna

Orrick

There are several Percivals scattered through the Harry Potter series, which might help transform the old-fangled, fussy image it has accrued. Actually, the original Percival was the one perfectly pure Knight of the Round Table, a worthy hero. The name was invented in the twelfth century by a poet named Chretien de Troyes, for his ideal knight in the poem Percevale, a Knight of King Arthur. 
 Percival is found in other forms of literature as well, including Wilkie Collins's The Woman in White, and Tennyson's "Idylls of the King" contains a section devoted to Sir Percival. Wagner transformed the name to Parsifal for his opera.
 Percy, which seems like a nickname for Percival but is really a stand-alone Norman place name, is beginning to attract some favorable attention from cutting-edge namers.

Percival

Petronella, and its shorter sister Petra, are both feminizations of Peter. While Petronella is a name with deep history, it's extremely rare. It was given to no baby girls on record in the US last year.

Petronella

Prothesia

Rohesia

Sabelina

Sibri

Siward

Thurston Howell was the snooty millionaire on Gilligan's Island, but these days such surname names don't have the same elitist air.

Thurstan

Theodorick

Torold

Trea

This name of a Roman emperor and of a sedating plant doesn't have much of a baby name future, unless you just like its strong, rhythmic sound. 

Valerian

Wade has never been outside the US Top 1000 for boys - there's a reason for that. It has a clean spelling, fresh sound and is neither too trendy (unlike Kade or Cade) or too old-school (like Richard or Albert). We think Wade is a winning name.

Wade

Chef Wolfgang Puck has helped soften this thunderous Germanic name; music-lovers will appreciate its association with Mozart, though the composer's middle name Amadeus is more appealing. 

Wolfgang

Dignified first name of poet W. H. Auden, less exposed than his currently stylish surname.

Wystan

Wentiliana

theresaelsmore's list "Abandoned and Come-Back Ready Medieval Names" of 69 great name ideas: Appoline - Wentiliana!

Abandoned and Come-Back Ready Medieval Names

Unusual with plenty of character and strength. These rare Midieval names have been in slumber for much too long and make for a fresh and delightful choice.