'mortality' originates from Late Latin, specifically the word 'mortalitas', where 'mort-' meant 'death' (from Latin 'mors' meaning 'death').

'mortality' changed from Late Latin 'mortalitas' into Old French 'mortalité' and then entered Middle English as 'mortalté', eventually becoming the modern English word 'mortality'.

Initially, it meant 'the condition of being mortal' or 'subject to death'; over time it also came to refer to 'the number or rate of deaths' and collective 'deaths' in particular contexts.