'gradually-altered' originates from the combination of 'gradually' and 'altered', where 'gradually' comes from the Latin 'gradualis', meaning 'step by step', and 'altered' from the Latin 'alterare', meaning 'to change'.

'Gradualis' transformed into the Old French 'graduel', and 'alterare' became 'alterer' in Old French, eventually forming the modern English 'gradually-altered'.

Initially, 'gradually' meant 'step by step', and 'altered' meant 'changed'. Together, they convey the idea of a slow and steady change.