A deposit made by each of two brokers, parties to a contract, when one is called up by the other. (Century Dict.)
1870. The broker’s power to buy on a margin depends upon the certainty that the collaterals will have a definite borrowing capacity…. The first clause of every contract for purchase by margin is that the relative per cent must be kept up…. What you pay down is called margin; but behind it lies your whole fortune.—James K. Medbery, ‘Men and Mysteries of Wall Street,’ pp. 56, 57, 66 (Boston).
