'nonimmune-mediated' is a compound formed from the prefix 'non-' (from Latin 'non' meaning 'not'), 'immune' (from Latin 'immunis' via Medieval Latin 'immunis', meaning 'exempt'), and 'mediated' (from Latin 'mediatus', past participle of 'mediare', based on 'medius' meaning 'middle').

'immune' changed from Latin 'immunis' into Medieval Latin and entered English as 'immune'; 'mediate' comes from Latin 'mediatus' → Old French/Medieval Latinate forms → Middle English 'mediate', with the past participle becoming 'mediated'; the modern compound 'nonimmune-mediated' is a recent scientific formation combining these elements.

Individually, 'immune' originally meant 'exempt' and 'mediate' related to 'being in the middle' or 'acting between'; combined in modern scientific usage the compound shifted to the specific sense 'not mediated by the immune system' (i.e., caused by non-immune mechanisms).