'unfairly-treated' originates from the combination of 'unfairly' and 'treated'. 'Unfairly' comes from 'un-' meaning 'not' and 'fair' meaning 'just or equitable'. 'Treated' is the past participle of 'treat', which comes from Old French 'traitier', meaning 'to deal with'.

'Unfairly' evolved from Middle English 'unfaire', and 'treated' from Middle English 'treted', both of which eventually became the modern English 'unfairly-treated'.

Initially, 'unfairly' meant 'not fair', and 'treated' meant 'dealt with'. Over time, 'unfairly-treated' evolved to mean 'subjected to unjust treatment'.