'theory-based' originates from the combination of 'theory' and 'based', where 'theory' comes from the Greek word 'theoria', meaning 'contemplation, speculation'.

'theoria' transformed into the Latin word 'theoria', and eventually became the modern English word 'theory'.

Initially, 'theoria' meant 'contemplation or speculation', but over time it evolved into its current meaning of 'a system of ideas intended to explain something'.