The olive tree and olive oil were were elements of great symbolism in Greece - it is a symbol of peace and prosperity; resurrection and hope.
Olive Oil / Olive Tree in religious scripture
Olive harvest http://www.historyforkids.org
Olive oil and Greek mythology
Olive Tree - Olive Oil - Ancient Greece
Anointing with Oil | Discover | First Fruits of Zion
Olive Oil in Ancient Greece
Olive oil and the Greek economy ... over 70% of the total Greek olive oil production is of extra-virgin quality