Really this is a lawyer using 2 words where 1 is enough
However, I would replicate the duality in English, even though in the case of a mortgage the 2 words effectively mean the same

In lending agreements, collateral is a borrower's pledge of specific property to a lender, to secure repayment of a loan.[1][2] The collateral serves as protection for a lender against a borrower's default—that is, any borrower failing to pay the principal and interest under the terms of a loan obligation. If a borrower does default on a loan (due to insolvency or other event), that borrower forfeits (gives up) the property pledged as collateral, with the lender then becoming the owner of the collateral. In a typical mortgage loan transaction, for instance, the real estate being acquired with the help of the loan serves as collateral. Should the buyer fail to pay the loan under the mortgage loan agreement, the ownership of the real estate is transferred to the bank. The bank uses a legal process called foreclosure to obtain real estate from a borrower who defaults on a mortgage loan obligation. A pawnbroker is an easy and common example of a business that may accept a wide range of items rather than just dealing with cash.

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Note added at 3 days6 hrs (2014-08-11 16:57:48 GMT)
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A secured loan is a loan in which the borrower pledges some asset (e.g. a car or property) as collateral for the loan, which then becomes a secured debt owed to the creditor who gives the loan. The debt is thus secured against the collateral — in the event that the borrower defaults, the creditor takes possession of the asset used as collateral and may sell it to regain some or all of the amount originally loaned to the borrower, for example, foreclosure of a home. From the creditor's perspective this is a category of debt in which a lender has been granted a portion of the bundle of rights to specified property. If the sale of the collateral does not raise enough money to pay off the debt, the creditor can often obtain a deficiency judgment against the borrower for the remaining amount. The opposite of secured debt/loan is unsecured debt, which is not connected to any specific piece of property and instead the creditor may only satisfy the debt against the borrower rather than the borrower's collateral and the borrower. Generally speaking, secured debt may attract lower interest rates than unsecured debt due to the added security for the lender; however, credit history, ability to repay, and expected returns for the lender are also factors affecting rates.[1]