Origins
The English word 'million' arrived relatively late in the language's history, borrowed in the late 14th century from Middle French 'million,' which itself came from Old Italian 'milione.' The Italian word is an augmentative form of 'mille' (thousand, from Latin 'mīlle'), created with the suffix '-one' that denotes something large or great — as in 'pallone' (a big ball, from 'palla') or 'minestrone' (a big soup, from 'minestra'). Thus 'milione' meant literally 'a big thousand' or 'a great thousand,' a characteristically pragmatic Italian coinage driven by the needs of medieval banking and commerce.
Before 'million' entered European languages, there was no standard word for this quantity in most vernaculars. Latin had 'deciēs centēna mīlia' (ten times a hundred thousand) — a cumbersome periphrasis reflecting the Roman numeral system's lack of a dedicated symbol or word for quantities above thousands. The medieval Latin 'milliō' (genitive 'milliōnis') was a back-formation from the Italian, not a classical Latin word. The ancient Greeks had 'myriás' (ten thousand, the source of English 'myriad') but no single word for a million; they would say 'a hundred myriads.'
The emergence of 'million' as a word is intimately connected to the rise of Italian banking in the 13th and 14th centuries. The great banking houses of Florence, Venice, and Genoa — the Bardi, Peruzzi, and Medici — handled financial transactions on a scale unprecedented in medieval Europe. They needed vocabulary for large numbers that Latin and the Romance vernaculars simply did not have. The augmentative formation 'milione' was a natural solution, and it spread rapidly through the international networks of Italian finance.
Development
The word's cultural dissemination was aided by its association with Marco Polo. His famous account of travels in Asia, composed around 1300, became known by the nickname 'Il Milione' — traditionally explained as a reference to the incredible, million-fold riches he described, though the nickname may actually derive from his family's name 'Emilione.' Regardless of the exact origin, the association between 'milione' and fabulous, almost unbelievable quantity helped embed the word in the European imagination.
The English borrowing appears in Chaucer's era, with early attestations in the late 1300s. The word was initially treated as somewhat exotic and was often used hyperbolically ('a million thanks') as much as literally. It was not until the expansion of international trade, colonial wealth, and eventually industrial capitalism that 'million' became a routine term in financial and demographic discourse.
The morphological pattern established by 'million' — using augmentative and multiplicative formations on Latin 'mīlle' — became productive in creating still larger number words. 'Billion' was coined in French in the 15th century, originally meaning 'a million million' (10¹²) in the so-called 'long scale' used in continental Europe, or 'a thousand million' (10⁹) in the 'short scale' adopted by English-speaking countries. 'Trillion,' 'quadrillion,' and higher formations followed the same pattern, combining Latin numerical prefixes with the '-illion' element extracted from 'million.'
Latin Roots
The base word 'mīlle' from which 'million' derives has its own rich legacy in English. 'Mile' comes from Latin 'mīlle passūs' (a thousand paces), the standard Roman unit of distance. 'Millennium' combines 'mīlle' with 'annus' (year). 'Millimeter' uses the metric prefix 'milli-' (a thousandth). And 'millionaire' — first attested in French in 1762 and in English shortly after — describes a person possessing a million units of currency, a word that would have been meaningless without the Italian banking innovation that created 'milione' five centuries earlier.
The etymology of Latin 'mīlle' itself remains uncertain. Unlike 'centum' (hundred), which can be confidently traced to PIE *ḱm̥tóm, 'mīlle' has no established Indo-European etymology. Some scholars have connected it to Greek 'mýrioi' (ten thousand, countless), but the phonological correspondence is weak. Others have suggested a pre-Indo-European substrate origin, reflecting early Italic contact with non-IE populations in the Italian peninsula. The uncertainty surrounding 'mīlle' contrasts sharply with the transparency of 'million's' derivation from it — we know exactly how 'million' was formed but not where its root word ultimately came from.