Morgaine

Variant of MORGAN (2), from a French form.

MORGAN (2)   female   Arthurian Romance
Modern form of Morgen, which was used by Geoffrey of Monmouth in the 12th century for the Arthurian sorceress Morgan le Fay, who was unnamed in earlier stories. Geoffrey probably did not derive it from the Welsh masculine name Morgan, which would have been spelled Morcant in his time. He may have based it on the Irish name MUIRGEN.
MUIRGEN   female   Irish, Irish Mythology
Means "born of the sea" in Gaelic. In Irish legend this was the name of a woman (originally named Líban) who was transformed into a mermaid. After 300 years she was brought to shore, baptized, and transformed back into a woman.
EQUIVALENTS
ARTHURIAN ROMANCE: Morgan, Morgen
FRENCH: Morgane
OTHER FORMS
IRISH MYTHOLOGY: Muirgen
IRISH: Muirgen, Muirín