The word fairy derives from Middle English faierie (also fayerye, feirie, fairie), a direct borrowing from Old French faerie (Modern French féerie) meaning the land, realm, or characteristic activity (i.e. enchantment) of the legendary people of folklore and romance called (in Old French) faie or fee (Modern French fée). This derived ultimately from Late Latin fata (one of the personified Fates, hence a guardian or tutelary spirit, hence a spirit in general); cf. Italian fata, Portuguese fada, Spanish hada of the same origin. Source.