'postfebrile' is formed from the Latin prefix 'post-' meaning 'after' and 'febrile' from Latin 'febris' meaning 'fever'.

'febrile' comes from Latin 'febrilis' (related to 'febris' = 'fever'), and the prefix 'post-' (Latin) was attached in English medical usage to create 'postfebrile' meaning 'after fever'.

Originally composed to denote timing 'after fever', the term has retained this specific medical meaning referring to conditions or signs occurring following a febrile episode.