Polynesia (n.)

peninsula south of Thrace, from Greek khersonesos "peninsula," etymologically "island connected to the mainland," from khersos "dry land, mainland" + nēsos "island," also "(flooded) land near a river, alluvial land," which is of uncertain origin; traditionally from PIE root sna- "to swim," but this is now generally rejected. "As words for 'island' differ from language to language, [nēsos] is probably an Aegean loan (note that Lat. insula is also of unclear origin)" [Beekes]. Compare isle.

Greek khersos is perhaps from PIE root *ghers- "to bristle" (see horror (n.)) if the Greek word first referred to "arid, stubbly land, and only later to land in opposition to water" [Beekes].

one of three large divisions of western Pacific islands, 1840, from French Mélanésie (by 1835); see melano- "black" + nēsos "island" (see Chersonese) + -ia. Modeled after Polynesia and meant to signify "the islands inhabited by blacks."

La Melanesia comprende la grande isola Australia, e quelle degli arcipelaghi di Salomone, di Lapèrouse, di Quiros, e dei gruppi della Nuova Caledonia, di Norfolk, e della Diemenin. A cagione dei Neri Oceanici, che, quasi esclusivamente, ne popolano le regioni, questa parte della Oceania ebbe dai moderni geografi e viaggiatori (il Graberg, il Rienzi, il d'Urville, ec.) il nome di Melanesia. [ "Corso di Geografia Universale," Firenze, 1839]

Related: Melanesian (1835, n., "a native of Melanesia;" 1840, adj., "of or belonging to Melanesia or the peoples inhabiting it").