Eilidh -Eilidh is a female name of Scottish and Gaelic origin possibly meaning wicker reed, basket or torch.
Endewyn -Endewyn is a girl's name of Welsh origin meaning "pleasant".
Epona -Epona was a Celtic Goddess associated with horses, mares and fertility. She was also adopted by the Romans. The name derived from the Gaulish word epos meaning "horse".
Estrild -Estrild contains the Norse hild meaning battled and may relate to Eostar, the Goddess of Dawn honored at the Spring Equinox. (An excellent name for a little warrior girl born at the spring Equinox.) or may related to Æsir, the Norse name for the race of Gods.
Evelyn -Evelyn is a name of Germanic origin that is used for both boys and girls but most often for girls in the US. It means "little bird" or perhaps "desired".
Fawn -Fawn is a girl's name from the English language referring to a young deer.
Gavin -Gavin is a Welsh name meaning "white hawk of battle".
Gawain -Gawain was the name of one of the knights of King Arthur's round table. The name means "white hawk of battle".
Grania -Grania is a Celtic name variously translated to mean "grain" "love" or "horror/terror".
Guinevere -Guinevere is the name of King Arthur's wife in the Arthurian legends. The Welsh form of this name is Gwenhwyfar and in modern English is Jennifer.
Gwydion -The name Gwydion may come from the Welsh for "ploughs" or "looms" or perhaps "trees". He was a magician of Welsh lore who excelled at the art of glamor, the father of Llew Llaw Gyffes and brother of Arianrhod.
Gwylfai -Gwilfye is a girl's name of Welsh origin meaning "May festival" referring to the first of May.
Hafgan -Hafgan is a Welsh name meaning "summer song". He is featured as the enemy of Arawn in the story of Pwyll's Descent into Annwn.
Hart -Hart is an English word meaning stag that can be used as a boy's name or a surname.
Jennifer -Jennifer is a Cornish variant of the name Guinevere which is itself a Middle English variant of the old Welsh name Gwenhwyfar which means "white" or "smooth" "fairy woman".
Of course Gwenhwyfar / Guinevere was King Arthur's wife.
Kai -Kai is a boy's name of Scottish origin meaning "fire". It also means "ocean" in Hawaiian and and "seashell" in Japanese and can be used for a girl as well.
Kevin -Kevin is a Gaelic name meaning "beautiful at birth".
Liadan -The name Liadán is a girl's name of Gaelic origin. It means "Grey lady" or "Grey poet".
You left off "Cory" which is pretty darned Celtic! lol
I was the only one in Catholic school without a saint's name and a nice nun told me I could be "St. Cory" one day… but I "drifted" and became a nice Pagan boy. lol