casualty

From casual, tracing back through Middle French casuel and Medieval Latin casualitas to Late Latin cāsuālis, 'happening by chance,' itself from Latin cāsus, 'event,' from cadere, 'to fall.'

It originally named any chance occurrence, good or bad, but over time narrowed to mean specifically an unfortunate event — especially the loss of a person.

It shares its root with case, both descending from Latin cāsus, 'event' or 'that which falls.'