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 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.