What does Sloane mean?
From the Irish surname Ó Sluaghadháin, built on 'sluagh' (host, army, raiding party). Authoritative sources gloss the root name as 'raid/raider'; 'warrior/man of arms' is a common popular reading of the 'army' sense.
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.