Origins
The word 'maize' is one of the earliest borrowings from any indigenous American language into a European one. It comes from Spanish 'maíz,' itself borrowed from Taino 'mahiz' (or 'mahís'), the term used by the Arawakan-speaking peoples of the Caribbean for the cereal grain that would become one of the most important food crops in human history.
Christopher Columbus recorded the word in his journal in November 1492, during his first voyage. When he encountered the Taino people of Hispaniola (modern Haiti and the Dominican Republic), one of the most notable features of their agriculture was a tall cereal plant with large, seed-bearing ears — completely unlike any grain known in the Old World. Columbus wrote that the natives called it 'mahiz,' and this Hispanicized form entered Spanish as 'maíz' almost immediately.
The Taino people belong to the Arawakan language family, one of the most widespread indigenous language families of the Americas. Despite their near-total destruction within decades of European contact — through disease, enslavement, and violence — the Taino language left a remarkable lexical legacy. In addition to 'maize,' English has borrowed 'barbecue' (from 'barbacoa,' a framework for cooking meat), 'hammock' (from 'hamaka'), 'canoe' (from 'canoa'), 'hurricane' (from 'hurakán'), 'tobacco' (from 'tabako'), 'savanna' (from 'sabana'), and 'iguana' (from 'iwana'), all through Spanish. These words are the most visible surviving trace of a people who were otherwise almost completely erased.
Development
Maize (Zea mays) was domesticated from a wild grass called teosinte in the Balsas River valley of southern Mexico approximately 9,000 years ago. By the time of European contact, it had spread from southern Canada to southern Chile, and was the dietary foundation of most American civilizations, including the Maya, Aztec, and Inca empires. The Nahuatl (Aztec) word for maize was 'tlāolli,' and the Quechua (Inca) word was 'sara' — neither of these more geographically and culturally significant terms became the international word, because the Caribbean Taino were the first indigenous Americans the Spanish encountered.
The word 'maize' spread from Spanish to virtually every European language: French 'maïs,' Italian 'mais,' German 'Mais,' Dutch 'maïs,' Russian 'кукуруза' (kukuruza — a different borrowing, possibly from Romanian or Turkish). Portuguese 'milho' is an exception: the Portuguese applied their existing word for millet (from Latin 'milium') to the new grain, rather than adopting the Taino term.
The relationship between 'maize' and 'corn' in English is a source of transatlantic confusion. In British English, 'corn' has always meant grain in general — wheat in England, oats in Scotland, any dominant cereal crop. When English colonists in North America encountered maize, they called it 'Indian corn' (grain of the Indians), which was later shortened to 'corn.' Thus American English 'corn' and British/international English 'maize' refer to the same plant, but 'corn' in its broader English sense means any grain at all. The King James Bible's references to 'corn' refer to wheat or barley, not maize, which did not exist in the Old World.