'undocumented' originates from the prefix 'un-' meaning 'not' and the word 'documented', which comes from Latin 'documentum', meaning 'lesson, proof'.

'documentum' transformed into the Old French word 'document', and eventually became the modern English word 'document'. The prefix 'un-' was added to form 'undocumented'.

Initially, 'documentum' meant 'lesson or proof', but over time, 'document' evolved to mean 'a written or printed paper'. 'Undocumented' now refers to the absence of such papers.