'justly-performed' originates from the combination of 'justly' and 'performed', where 'justly' means 'in a fair manner' and 'performed' means 'executed or carried out'.

'Justly' comes from the Old French 'juste', and 'performed' from the Old French 'parformer', both of which were adopted into Middle English.

Initially, 'justly' meant 'in accordance with justice', and 'performed' meant 'to carry out', which has remained consistent in modern usage.