'casualty' originates from Old French, specifically the word 'casualté', where the root ultimately comes from Latin 'casus' meaning 'chance' or 'event'.

'casualty' changed from Old French 'casualté' (and Medieval Latin 'casualitas') and eventually became the modern English word 'casualty'.

Initially, it meant 'an event or chance occurrence' (from Latin); over time it evolved to mean 'a person injured, killed, or lost' and, by extension, 'a loss or damage'.