What does Darcy mean?
Two distinct origins: as an Irish name it anglicizes O Dorchaidhe, from 'dorcha' meaning 'dark', giving 'dark one'; as an English/Norman name it is the aristocratic d'Arcy, a locational surname meaning 'from Arcy' in Normandy, with no 'dark' sense. Both are genuine; flag which is intended.
What does Leannan mean?
From the Irish and Scottish Gaelic leannan (leannán) 'lover, sweetheart, darling', a diminutive of leann 'affection, love'. Familiar from the folklore figure leannan sidhe, the fairy lover.