'idiot' originates from Greek, specifically the word 'idiōtēs' (from 'idios'), where 'idios' meant 'private, one's own'.

'idiōtēs' passed into Late Latin as 'idiota' and Old French, then into Middle English as 'idiot(a)', eventually becoming modern English 'idiot'.

Initially, it meant 'a private person or layman (unskilled or uninvolved in public affairs)'; over time it evolved into the current meaning 'a very foolish or unintelligent person'.