'autoimmunity' originates from Modern English, specifically the combination of the prefix 'auto-' from Greek 'autos' meaning 'self' and 'immunity' from Latin 'immunitas' (from 'immunis') where 'immunis' meant 'exempt, free from service or duty'.

'immunity' came into English via Latin 'immunitas' and Old French 'immunité' before appearing in Middle and Modern English; the combining form 'auto-' comes from Greek 'autos'. The compound 'autoimmunity' was coined in medical literature in the early 20th century as immunology developed.

Initially, the parts meant 'self' and 'exemption/protection'; over time the compounded term came to mean specifically an immune reaction directed against the self (often with pathological implications), rather than protection or exemption.