'post-exposure' originates from Latin elements: the prefix 'post-' (Latin 'post') meaning 'after', and 'exposure' ultimately from Latin 'exponere' (ex- 'out' + ponere 'to place'), which led to Old French/Middle English forms and modern English 'expose'/'exposure'.

'exponere' in Latin developed into Old French forms like 'exposer'/'exposur' and into Middle English as 'exposure'; the prefix 'post-' passed from Latin into English. The modern compound 'post-exposure' arose by joining 'post-' and 'exposure', especially in medical usage.

Initially, 'exposure' meant 'the act of placing out or exposing'; over time it came to mean 'exposure to something (e.g., radiation, infection)'. Combined with 'post-', the compound evolved to mean 'occurring after exposure', frequently used for medical or health contexts (e.g., post-exposure prophylaxis).