/ˈkæʒ.u.əl.ti/
[noun] A person who is killed or injured in a war, accident, or disaster. It can also refer to something that is lost or badly damaged as a result of an event.
The word 'casualty' shares its soul with 'chance' — both descend from the Latin word for 'a fall of the dice'.
At the heart of 'casualty' lies the Latin word 'casus', meaning 'a fall' or 'a chance event'. This word came from the Latin verb 'cadere', which meant 'to fall'. The Romans used 'casus' to describe anything that happened by chance — a falling of fortune, so to speak, as unpredictable as a stone tumbling from a cliff. From this root, Medieval Latin scholars built the adjective 'casualis', meaning 'subject to chance' or 'happening by accident', which then passed into Old French as 'casuel' before crossing into Middle English.
In the 15th century, English writers began using the word 'casualty' — derived from Medieval Latin 'casualitas' — to mean an accident or a chance misfortune. Early uses were broad and philosophical: a casualty was simply something unfortunate that had happened without warning, a random blow dealt by fate. There was no specific military meaning yet. Life itself, in its unpredictability, was full of casualties in this older sense.
The military meaning arrived gradually, growing more specific as the language of organised warfare became more precise. By the 16th and 17th centuries, military commanders and record-keepers needed a clear word for soldiers lost during battle — not just those killed outright, but also the wounded, the captured, and the missing. 'Casualty' filled that role perfectly, because every soldier lost was, in a sense, a victim of chance. The randomness of an arrow or a cannonball made 'casualty' feel exactly right.
It is worth pausing on the remarkable family of words that share the Latin root 'cadere'. Following the chain carefully: Latin 'cadere' gave rise to 'casus' (a fall, a chance), which became Medieval Latin 'casualis', then Old French 'casuel', then English 'casual' — meaning something relaxed, unplanned, or done by chance. The same Latin 'casus' also passed through Old French as 'cas', entering English as 'case' (as in a legal case or a matter under consideration — something that 'fell' before a court). Further along, Latin 'cadere' became Old Italian 'cadere', giving us 'cadence', the rhythmic fall of sound or movement. Even 'accident' connects here: Latin 'accidere' (meaning 'to fall upon') combined 'ad-' (to) and 'cadere' (to fall), flowing into Old French 'accident' and then directly into English.
Today, 'casualty' has stretched into everyday civilian life. We speak of the 'casualties' of economic downturns, of truth being 'the first casualty of war' — a famous phrase often attributed to the ancient world — and of hospital casualty departments where the injured are treated. That last use, common in British English, brings us full circle: a place dedicated entirely to the people whom chance has struck down. The word has kept its essential meaning across six centuries, still whispering of randomness, misfortune, and the unpredictable fall of fate.