Certain investment active requires guarantee deposits (e.g., certain derivatives positions). By law, these deposit must also earn a minimum return preventing the deposit taker from profiting unfairly or the investor from not earning some yield on those"idle" funds

My only disagreements with Paul's answer: the better term is 'security deposit' (it's collateral), and the single preposition 'sur' in the French is a bit elliptical. In practice, the broker who takes your deposit is going to call it 'margin', but everyone knows that it functions as a security deposit, and the regulator can be expected to write rules using ordinary legal language. Lastly, 'compensation' is too easily confused with netting and clearing; this is about crediting interest on the deposit.