'ex-service' originates from Latin and Old French elements: the prefix 'ex-' originates from Latin, specifically the word 'ex', where 'ex' meant 'out of, former'; 'service' originates from Old French 'service', ultimately from Latin 'servitium', where 'servitium' meant 'servitude, service'.

'service' passed from Latin 'servitium' into Old French as 'service' and then into Middle English as 'service'; the English prefix 'ex-' (from Latin 'ex') was later attached in modern English to form the compound 'ex-service' meaning someone formerly in a service (especially the armed forces).

Initially the elements signified 'out of service' or 'former service'; over time the compound came to be used specifically for people formerly in the armed forces (i.e., 'veteran').