archipelago
Pronunciation: /ˌɑːkɪˈpɛləgəʊ/
noun ( plural archipelagos or archipelagoes)

Origin:
early 16th century: from Italian arcipelago, from Greek arkhi- 'chief' + pelagos 'sea'. The word was originally used as a proper name (the Archipelago 'the Aegean Sea'): the general sense arose because the Aegean Sea is notable for its large numbers of islands

Spelling help
The plural of archipelago can be spelled either archipelagos or archipelagoes.