From Glossary of Meteorology
The prevailing northerly winds in summer in the eastern Mediterranean and especially the Aegean Sea; basically similar to monsoon and equivalent to the maestro of the Adriatic Sea.
According to the ancient Greeks, the etesians blow for 40 days, beginning with the heliacal rising of Sirius. They are associated (along with the seistan and shamal) with the deep low pressure area that forms in summer over northwest India. They bring clear skies and dry, relatively cool weather. In Greece the etesian wind is locally named the sleeper. In Turkey it is the meltém. The Romans used the word also for the southwest monsoon of the Arabian Sea.