'perpetually-maintained' originates from the combination of 'perpetual' and 'maintain', where 'perpetual' comes from Latin 'perpetuus' meaning 'continuous', and 'maintain' from Old French 'maintenir', meaning 'to hold in hand'.

'perpetual' changed from Latin 'perpetuus' to Old French 'perpetuel', and eventually became the modern English word 'perpetual'. 'Maintain' evolved from Old French 'maintenir' to Middle English 'maintainen', and eventually became 'maintain'.

Initially, 'perpetual' meant 'continuous' and 'maintain' meant 'to hold in hand', but over time, 'perpetually-maintained' evolved to mean 'continuously kept in good repair'.