'autodiagnosis' originates from Greek, specifically the words 'αὐτός' and 'διάγνωσις', where 'αὐτός' meant 'self' and 'διάγνωσις' meant 'a distinguishing' or 'diagnosis'.

'diagnosis' passed from Greek διάγνωσις into Latin and then into Middle English as 'diagnosis'; the combining form 'auto-' from Greek αὐτός was appended in modern English to form compounds such as 'autodiagnosis'.

Initially composed of roots meaning 'self' + 'distinguishing', the compound has come to mean specifically 'the act of diagnosing oneself' in modern usage.