'arbitrement' originates from Old French, specifically the word 'arbitrement', where the root 'arbitre' (from Latin 'arbiter') meant 'judge' and Latin 'arbitrium' meant 'judgment or decision'.

'arbitrement' changed from Latin 'arbiter'/'arbitrium' into Old French as 'arbitrement' and entered Middle English (alongside forms like 'arbitrament'), eventually surviving in English as the rare/archaic word 'arbitrement'.

Initially it meant 'judgment or the power to judge', but over time it evolved into its current (specialized) meaning of 'settlement or decision given by arbitration'.