This apparent rogue word continues to baffle etymologists. It has been in use since 1502 according to the OED, describing a mass of islands surrounded by sea, as in the Aegean and similar archipelagos in the Pacific and Indian Oceans e.g. the Philippines. Pelagos is Greek for sea and the prefix archi- is Greek for chief or pre-eminent, as in archbishop. Therefore, it should mean the chief or pre-eminent sea, which for the Greeks would of course be the Aegean with its mass of islands. The major problem with this is that there is no record of the word archipelago in either Ancient or Medieval Greek. Also, archipelago describes land i.e. the islands, rather than the sea around them. Because there is no citation for archipelago in either Ancient or Medieval Greek and the word is first cited in English in 1502, the OED ascribes an Italian origin, which only deepens the mystery. The archipelago with the most islands in the world is off the east coast of Sweden.