'extensively' originates from Latin, specifically the word 'extensus,' where 'ex-' meant 'out' and 'tendere' meant 'to stretch.' 'Checked' comes from Old French 'eschequier,' meaning 'to inspect or verify.'

'extensively' evolved from the Latin 'extensus' through Middle English, while 'checked' transformed from Old French 'eschequier' to the modern English 'check.'

Initially, 'extensively' meant 'stretched out,' but over time it evolved into its current meaning of 'in a comprehensive manner.' 'Checked' has largely retained its original meaning of 'inspected or verified.'