'justly-retained' originates from the combination of 'justly' and 'retained'. 'Justly' comes from the Old French 'juste', meaning 'fair', and 'retained' from the Latin 'retinere', meaning 'to hold back'.

'Justly' evolved from the Old French 'juste', and 'retained' from the Latin 'retinere', eventually forming the modern English compound 'justly-retained'.

Initially, 'justly' meant 'in a fair manner', and 'retained' meant 'held back'. Together, they convey the idea of something being kept in a fair manner.