'well-documented' originates from English, combining the adverb 'well' with the past-participle adjective 'documented'; 'document' originates from Latin, specifically the word 'documentum,' where 'docēre' meant 'to teach; to show.'

'documentum' passed into Old French as 'document,' then into Middle English 'document'; English formed the verb 'document,' whose past participle 'documented' was used adjectivally; Modern English then combined 'well' + 'documented' to yield 'well-documented.'

Initially, 'documentum' meant 'lesson; proof; example,' later narrowing to 'written record/document'; 'documented' came to mean 'recorded in documents,' and the compound 'well-documented' evolved to mean 'amply supported or thoroughly recorded/described.'