'persistently-kept' originates from the combination of 'persistent' and 'kept', where 'persistent' comes from Latin 'persistens', meaning 'continuing steadfastly', and 'kept' is the past participle of 'keep', from Old English 'cēpan', meaning 'to seize or hold'.

'persistens' transformed into the English word 'persistent', and 'cēpan' evolved into 'keep', eventually forming the modern English term 'persistently-kept'.

Initially, 'persistent' meant 'continuing steadfastly', and 'kept' meant 'to hold', evolving into the current meaning of 'maintained with persistence'.