'equal-value' originates from English as a compound of 'equal' and 'value', where 'equal' ultimately derives from Latin 'aequalis' (via Old French/Latin) meaning 'even, level', and 'value' ultimately derives from Old French 'valeur' (from Latin 'valere') meaning 'to be worth'.

'equal' comes from Latin 'aequalis' which passed into Old French and Middle English as 'equel'/'equal', and 'value' comes from Old French 'valeur' (from Latin 'valere'); the modern compound 'equal-value' formed in modern English by joining these two words to describe equivalence of worth.

Initially the roots meant 'even/level' (for 'equal') and 'to be worth' (for 'value'); combined as a modern English compound they specifically express the idea 'having the same worth', a meaning consistent with the original elements.