What does the word "academy" mean?

In the myths of Ancient Greece, there is a hero named Academus, who became famous for helping the twins Castor and Pollux free Helen, who had been abducted by Theseus. One of the gardens in Athens, where Academus was supposedly buried, was named in honor of this hero. The Garden of Academus was chosen for his walks and conversations by the great philosopher Plato (427–347 BC), a student of Socrates and the teacher of Aristotle. Plato's philosophical school was the first to be called an "academy."