I’m looking for names similar to [name_f]Beatrix[/name_f], [name_f]Cecily[/name_f], [name_f]Elvira[/name_f], [name_f]Rowena[/name_f], [name_f]Sybil[/name_f], etc…
These give me a medieval feel (I’m not entirely sure whether they are ‘legitimately’ medieval names or not though…):
[name_f]Alys[/name_f]
Gloriana
[name_f]Enid[/name_f]
Eupraxia
[name_f]Annora[/name_f]
[name_f]Basilia[/name_f]
[name_f]Imogene[/name_f]
[name_f]Leticia[/name_f]
[name_f]Hilda[/name_f]
[name_f]Felicia[/name_f]
[name_f]Adeline[/name_f]/[name_f]Adelina[/name_f]
[name_f]Judith[/name_f]
[name_f]Adelaide[/name_f]
[name_f]Sabina[/name_f]
[name_f]Muriel[/name_f]
[name_f]Clothilde[/name_f]
[name_f]Isolda[/name_f]
[name_f]Mathilde[/name_f]
Loreena
[name_f]Margery[/name_f]
Rohese/Rohesia
[name_f]Celestine[/name_f]
[name_f]Guinevere[/name_f]
[name_f]Gisela[/name_f]
Lunet
[name_f]Agnes[/name_f]
[name_f]Millicent[/name_f]
Jocosa
[name_f]Melisende[/name_f]
[name_f]Leda[/name_f]
[name_m]How[/name_m] about these? I hope you find just what you are looking for, even if some of these might not be true Medieval names. Not positive in these, but here is my attempt:
*[name_f]Adelaide[/name_f]
*[name_f]Amabel[/name_f] (Yes, with a “m”)
*[name_u]Clare[/name_u]
*[name_f]Clotilde[/name_f]
*[name_f]Elspeth[/name_f]
*[name_f]Iris[/name_f]
*[name_f]Gertrude[/name_f]
*[name_f]Octavia[/name_f]
*Ludmilla
*[name_f]Portia[/name_f]
*[name_f]Rosaline[/name_f], [name_f]Rosalind[/name_f], [name_f]Rosalie[/name_f], [name_f]Rosalia[/name_f] (Some of these [name_f]Rose[/name_f] variations are ancient Catholic saints and/or appear in works by [name_m]Shakespeare[/name_m].)
*[name_f]Viola[/name_f]
The only medieval name I know off the top of my head is Mevanou, which is a medieval form of [name_f]Myfanwy[/name_f].
[name_u]Love[/name_u] this thread!
Here are some “mediaeval” names I stumbled across…
Faerydae (gift from the fairies…love it!)
Faylinn ([name_f]Fairy[/name_f] kingdom)
Forestyne (of the forest)
Goldwine
[name_f]Marigold[/name_f]
[name_f]Isabeau[/name_f]
Ailith
[name_f]Arietta[/name_f]
[name_f]Eglantine[/name_f] (wild rose)
Mercia
[name_f]Merry[/name_f]
Rhoswen
Sebille (a fairy)
[name_f]Titania[/name_f]
Auberee
Clarimond
[name_f]Heloise[/name_f]
[name_f]Oriel[/name_f]
Richenda/ Richenza
[name_f]Rosalind[/name_f]/ [name_f]Rosalinda[/name_f]
Helewise
Mazelina
Sabelina
[name_f]Gisela[/name_f]/ [name_f]Giselle[/name_f]
Adallinda
[name_f]Elira[/name_f]
[name_f]Clemence[/name_f]
[name_f]Petronia[/name_f]
Clarissant
Igraine
Lyndara
[name_f]Modesty[/name_f]
Quinevere
Roberge
Splendora
Most of these names remind me of names of adults in the [name_m]Harry[/name_m] [name_m]Potter[/name_m] series.
Here’s an alphabetical listing of every name ever mentioned in the wizarding world, including ones of historical and famous wizards and witches (obviously in the series). I think Rowling is a genius with names.
[name_f]Cecily[/name_f] is gorgeous.
Other suggestions…
[name_f]Clothilde[/name_f]
[name_f]Isolde[/name_f]
[name_f]Morgana[/name_f]
[name_f]Marielle[/name_f]
Clarimond
Clarissant
Elysant/Elysande
[name_f]Melisande[/name_f]
[name_f]Melisende[/name_f]
[name_f]Margery[/name_f]
[name_f]Celestina[/name_f]
[name_f]Rosaline[/name_f]
[name_f]Griselda[/name_f]
[name_f]Romilda[/name_f]
[name_f]Rosamund[/name_f]
[name_f]Sunniva[/name_f]
[name_f]Ottilie[/name_f]
[name_f]Melusine[/name_f]
Briseida/Briseis
[name_f]Novella[/name_f]
[name_f]Dorothea[/name_f]
[name_f]Avalon[/name_f]
[name_f]Elysia[/name_f]
Hawise
[name_f]Blanchette[/name_f]
Odalie
[name_f]Sabra[/name_f]
Eldreth
[name_f]Ardyth[/name_f]
Sorry for any duplicates…
[name_m]How[/name_m] about-
[name_f]Cornelia[/name_f]
[name_f]Amoret[/name_f]
[name_f]Leonora[/name_f]
[name_f]Branwen[/name_f]
[name_f]Gwendolen[/name_f]
[name_f]Guinevere[/name_f]
[name_f]Eluned[/name_f]
[name_f]Euphemia[/name_f]
[name_f]Kassiani[/name_f]
[name_f]Rhonwen[/name_f]
[name_f]Minerva[/name_f]
[name_f]Drusilla[/name_f]
[name_f]Dominica[/name_f]
[name_f]Constantina[/name_f]
[name_f]Octavia[/name_f]
[name_f]Mirabel[/name_f] (my favorite)
[name_f]Mazarine[/name_f]
[name_f]Philippa[/name_f]
[name_f]Idonea[/name_f]
[name_f]Luanda[/name_f]
[name_f]Agnes[/name_f]
[name_f]Blythe[/name_f]
[name_f]Blanche[/name_f]
[name_f]Cicely[/name_f]
Clarimond
[name_f]Charity[/name_f]
[name_f]Clemence[/name_f]
[name_f]Clemency[/name_f]
[name_f]Constance[/name_f]
[name_f]Esther[/name_f]
[name_f]Eunice[/name_f]
Gwenllian
Kynborow
[name_f]Lettice[/name_f]
[name_f]Magdalen[/name_f]
[name_f]Martha[/name_f]
Ismeria
[name_f]Millicent[/name_f]
[name_f]Philippa[/name_f]
[name_f]Priscilla[/name_f]
[name_f]Prudence[/name_f]
[name_f]Sidonie[/name_f]
[name_f]Susanna[/name_f]
[name_f]Thomasin[/name_f]
[name_f]Agatha[/name_f]
[name_f]Christiana[/name_f]
[name_f]Clarice[/name_f]
[name_f]Evita[/name_f]
[name_f]Isolde[/name_f]
[name_f]Idony[/name_f]
[name_f]Isadora[/name_f]
Helewise
Godeleva
[name_f]Mabel[/name_f]
[name_f]Osanna[/name_f]
[name_f]Petronilla[/name_f]
[name_f]Susan[/name_f]
[name_m]Christian[/name_m]
[name_f]Frances[/name_f]
[name_f]Ursula[/name_f]
[name_f]Christabel[/name_f]
[name_f]Temperance[/name_f]
[name_f]Dorcas[/name_f]
[name_f]Maud[/name_f]
[name_f]Benedicta[/name_f]
[name_f]Bethia[/name_f]
[name_f]Mariella[/name_f]
Wyborough
[name_f]Augustina[/name_f]
Etheldreda
The following lists might be helpful for you 
http://www.britishbabynames.com/blog/2013/05/terrifically-tudor.html
If you’re looking to go way, way back, here is a site that will help: Names in the Low Countries before 1150
The non-Germanic choices will generally be the most usable options.
There’s also this resource too — Medieval Names Archive
The table of contents allows you to select a specific culture and lists name articles that provide insights into names from the medieval period. I do apologize in advance for the massive amount of time that this site will take away from you. 
ETA: Oops, forgot the link –> Medieval Naming Guides: English
This link was the first thing I thought of when I saw the title of this thread It’s my go-to website for naming characters when writing, and I heartily second the recommendation!
Here’s some feminine names from a few of the Medieval lists, like “Feminine Given Names in
A Dictionary of English Surnames” Feminine Given Names in DES: Introduction
Amicia
Betryse
[name_f]Celestina[/name_f]
[name_f]Leticia[/name_f]
Isemay
Margeria
[name_u]Love[/name_u] this thread! I’ve recently gotten into Medieval names, and I really enjoy their feel. Some I think are particularly stunning are:
[name_f]Adelais[/name_f] (sometimes spelled [name_m]Ad[/name_m]élais, [name_f]Adela[/name_f]ïs, Adelasia, Azalaïs)
[name_f]Amelina[/name_f] (diminutive of [name_f]Amalia[/name_f] or [name_f]Emma[/name_f])
Ancrett (variation of Anchoret)
Athelesia (variant of [name_f]Adela[/name_f])
Barsabe (variant of [name_f]Bathsheba[/name_f])
[name_f]Bassilly[/name_f] (feminization of [name_m]Basil[/name_m])
Berengaria (feminization of Bérenger, of Germanic origins, meaning “bear + spear”)
Cyneburg (Anglo-[name_m]Saxon[/name_m], from some unknown element and “fortress”)
Edborough (variant of Eadburg, mean “rich fortress”)
Elisota (variantion of [name_f]Alice[/name_f], a name derived from [name_f]Adelaide[/name_f])
[name_f]Elspet[/name_f] (variant of [name_f]Elizabeth[/name_f])
Emony (variantion of [name_f]Emeny[/name_f] of unknown origins)
Evelune (a variant of [name_f]Eva[/name_f])
Everild (from the Anglo-[name_m]Saxon[/name_m] name Eoforhild, meaning “boar + battle”)
[name_f]Galiena[/name_f]
[name_f]Idony[/name_f] (Norse, [name_f]Idonea[/name_f] is also a variant)
[name_f]Isolde[/name_f] (possibly meaning “fair aspect”)
[name_f]Jacobina[/name_f] (feminization of [name_m]Jacob[/name_m])
Lewena (a variation of Leofwynn, meaning “dear + friend”)
Loveday
[name_f]Maude[/name_f] (variantion of [name_f]Matilda[/name_f])
[name_f]Marjorie[/name_f] (spelling variation of [name_f]Margery[/name_f], derived from [name_f]Margaret[/name_f])
Midwinter
Mottie (diminutive of [name_f]Williamina[/name_f], feminization of [name_m]William[/name_m])
Moggy (diminutive of [name_f]Margaret[/name_f])
Nycaise (feminization of [name_m]Nicasius[/name_m], meaning “victory” in Greek)
[name_f]Osanna[/name_f] (variantion of [name_f]Hosanna[/name_f])
[name_f]Philomena[/name_f]
Richenza (variantion of [name_f]Richarda[/name_f], feminization of [name_m]Richard[/name_m])
Rohesia (means “horse” or “fame”)
Sabelina (possibly a variation of [name_f]Isabel[/name_f])
Scholastica
Sedille (I’m assuming this is pronounced syd-dee)
[name_f]Sibyl[/name_f] (Greek for “prophetess”)
[name_f]Sidony[/name_f] (means “from Sidon” or Greek “winding-sheet”)
[name_f]Suky[/name_f] (diminutive of [name_f]Susannah[/name_f])
[name_f]Sunniva[/name_f]
Sweetlove (also Sweeting)
Tatsy (diminutive of [name_f]Elizabeth[/name_f])
[name_f]Thomasina[/name_f] (feminization of [name_m]Thomas[/name_m])
Wander (variation of [name_f]Guinevere[/name_f])
Wilmot (variation of [name_f]Williamina[/name_f], feminization of [name_m]William[/name_m])
[name_f]Melisande[/name_f]
[name_f]Carlotta[/name_f]
[name_f]Ghislaine[/name_f]
[name_f]Elke[/name_f]
Names ending in hilde were quite common. In a book I read there was [name_f]Gunhilde[/name_f] and Rothilde (not sure if this is how it’s spelled)