'equitably-determined' originates from the combination of 'equitably' and 'determined'. 'Equitably' comes from the Latin word 'aequitas', meaning 'fairness', and 'determined' comes from the Latin 'determinare', meaning 'to set bounds'.

'Equitably' evolved from the Old French 'equité', and 'determined' from the Old French 'determiner'. The combination of these words in modern English forms 'equitably-determined'.

Initially, 'equitably' meant 'in a manner of fairness', and 'determined' meant 'decided'. Together, they have maintained the meaning of 'decided in a fair manner'.