"the East Indies," 1850, from Indo- "India" + Greek nēsos "island" (see Chersonese) + -ia. Formerly called Indian Archipelago or East Indies Islands (see Indies). Related: Indonesian "of or from the East Indies" (1850).
peninsula south of Thrace, from Greek khersonesos "peninsula," from khersos "dry land" + 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.
D. Harper. “Etymology of Indonesia.” Online Etymology Dictionary. https://www.etymonline.com/word/Indonesia (accessed $(datetime)).
Definitions of Indonesia
a republic in southeastern Asia on an archipelago including more than 13,000 islands; achieved independence from the Netherlands in 1945; the principal oil producer in the Far East and Pacific regions;
Synonyms: Republic of Indonesia / Dutch East Indies