One of the hinged flaps on the trailing edge of a wing of an aeroplane for maintaining or restoring its balance when flying. From the French. aileron, diminutive of aile wing. First appearance in English in1909.
Oxford English Dictionary, Second Edition, 1989

And in case you'd like to improve your vocabulary in a few other languages...
French - Aileron
Italian - Alettone
Spanish - Alerón
German - Querruder
Japanese - エルロン