'justly-done' originates from the English word 'justly,' meaning 'in a fair manner,' and 'done,' meaning 'completed or performed.'

'Justly' and 'done' have been used in English since the Middle Ages, with 'justly' deriving from the Latin 'justus' and 'done' from the Old English 'don.'

Initially, 'justly' meant 'in accordance with justice,' and 'done' meant 'completed.' Together, they have maintained the meaning of 'completed in a fair manner.'