'well-researched' originates from the combination of 'well,' meaning 'in a good or satisfactory way,' and 'researched,' the past participle of 'research,' which comes from the Old French 'recercher,' meaning 'to seek out or search closely.'

'researched' changed from the Old French word 'recercher' and eventually became the modern English word 'research.'

Initially, 'research' meant 'to seek out or search closely,' but over time it evolved into its current meaning of 'systematic investigation or study.'