October is the second of the four 'wrong number' months that close out the Western calendar, its name proclaiming it the eighth month when it is in fact the tenth. This two-month discrepancy, identical to September's, is the enduring signature of the Roman calendar's evolution from a ten-month agricultural cycle to a twelve-month civil year.
The Latin 'Octōber' derives from 'octō' (eight), with the same '-ber' suffix found in September, November, and December. The numeral 'octō' descends from Proto-Indo-European *oḱtṓw (eight), a word of remarkable stability across the Indo-European family: Sanskrit 'aṣṭā,' Greek 'oktṓ,' Gothic 'ahtau,' Old Irish 'ocht,' Welsh 'wyth,' and Lithuanian 'aštuoni' all descend from the same source. The English words 'octave,' 'octopus,' 'octagon,' 'octet,' and 'octane' all share this root.
In the original calendar of Romulus, October was indeed the eighth month, falling between September (seventh) and November (ninth) in a year that ran from March through December. The addition of January and February — traditionally attributed to Numa Pompilius around 713 BCE — shifted October to the tenth position without any change to its name. As with the other numerical months, no Roman administration ever undertook the seemingly simple task of renaming the month to match its actual position, a fact that reveals how deeply embedded calendar names become in the fabric of daily life.
The emperor Domitian renamed October 'Domitianus' in his own honor, paralleling his renaming of September as 'Germanicus.' The emperor Commodus, in his grandiose scheme of renaming all twelve months after his accumulated titles, changed October to 'Invictus' (Unconquered). As with all such imperial renamings except July and August, these changes were immediately revoked by the Senate upon each emperor's death, and 'Octōber' endured.
The English word 'October' entered the language in Old English, borrowed directly from Latin. The Anglo-Saxons called this month 'winterfylleþ' (winter full-moon), the month in which the first full moon of winter appeared, signaling the beginning of the cold season. Bede recorded this name in his 'De Temporum Ratione' (725 CE), noting that winter was reckoned to begin in October in the Anglo-Saxon reckoning — considerably earlier than the modern astronomical definition.
October's cultural associations are shaped by its position at the heart of autumn in the Northern Hemisphere. The harvest, the changing of leaves, and the shortening of days give October a character of ripeness shading into decline. In the Christian liturgical calendar, October has no single dominant feast comparable to Christmas or Easter, but it was designated as the Month of the Rosary by Pope Leo XIII in 1883.
The most significant cultural event associated with October in the modern English-speaking world is Halloween (October 31), which derives from the eve of the Christian feast of All Saints' Day (November 1). Halloween's roots, however, reach back to the Celtic festival of Samhain, which marked the end of the harvest season and the beginning of the 'darker half' of the year. The Celts believed that on the night of Samhain, the boundary between the living and the dead grew thin, allowing spirits to pass between worlds. This pre-Christian festival, Christianized as All
In political history, October carries the weight of revolution. The 'October Revolution' of 1917, which brought the Bolsheviks to power in Russia, actually occurred on November 7 by the Gregorian calendar — but Russia was still using the Julian calendar, in which the date was October 25. The name 'October Revolution' thus preserves a calendrical ghost: the old Julian reckoning that Russia finally abandoned in February 1918.
Germany's Oktoberfest, the world's largest folk festival, bears October's name despite predominantly taking place in September. The festival was first held in October 1810 to celebrate the marriage of Crown Prince Ludwig of Bavaria to Princess Therese of Saxe-Hildburghausen, but over the decades it was gradually moved earlier to take advantage of warmer September weather. The name, however, stuck — another instance of a calendar name outliving the circumstances that created it.