'autoreactivity' originates from a compound formation using Greek and English elements: Greek 'autós' (aut- / 'auto-') meaning 'self' and English 'reactivity' (from Latin/English roots related to 'react') where 'autós' meant 'self' and the root of 'react' meant 'to act or respond'.

'reactivity' derives from the verb 'react' (from Latin components 're-' + stem related to 'agere' meaning 'to do/drive') that entered English via post-classical usage; the modern compound 'autoreactivity' developed in 20th century scientific English by prefixing 'auto-' to 'reactivity' to indicate 'self-directed reactivity'.

Initially, related terms like 'reactivity' meant 'capacity to respond to a stimulus'; over time the compound 'autoreactivity' came to specify responses directed at the self (i.e., immune reactions against self-components).