C16 (meaning: the Aegean Sea): from Italian arcipelago, literally: the chief sea (perhaps originally a mistranslation of Greek Aigaion pelagos the Aegean Sea), from archi- + pelago sea, from Latin pelagus, from Greek pelagos
c.1500, from Italian arcipelago "the Aegean Sea" (13c.), from Greek arkhipelagos, from arkhi- "chief" (see archon) + pelagos "sea" (see pelagic). The Aegean Sea being full of island chains, the meaning was extended in Italian to "any sea studded with islands." Klein, noting the absence of arkhipelagos in ancient or Medieval Greek (the modern word in Greek is borrowed from Italian) believe it is an Italian mistake for Aigaion pelagos "Aegean Sea" (Medieval Latin Egeopelagus), or influenced by that name.