'immune-mediated' originates from modern English, formed from the adjective 'immune' and the past-participle adjective 'mediated'. 'Immune' ultimately comes from Latin 'immunis', where 'immunis' meant 'exempt from public service or burden'. 'Mediated' comes via English from Latin 'mediatus', the past participle of 'mediare', where the root 'medius' meant 'middle'.

'immune' entered English via Latin 'immunis' (and Old French influences) to become modern English 'immune'. 'Mediate' developed from Latin 'medius' → Medieval Latin 'mediare' → Middle English 'mediate', with 'mediated' as the past participle used adjectivally. The compound 'immune-mediated' is a modern technical formation combining the two.

Individually, 'immune' originally meant 'exempt' and 'mediate/mediated' originally meant 'placed in or acting through the middle'. Over time the combined modern usage came to mean 'caused or carried out by the immune system', a technical medical sense.