Final answer:
The Louisiana Law allowing a borrower to put up just one item as collateral for a loan is called the Ne Varietur doctrine, where only the asset specified in the agreement is at risk in case of default.
Step-by-step explanation:
The Louisiana Law that allows a borrower to agree to only put up one "thing" for a loan and not all "things" is referred to as the Ne Varietur doctrine. This concept pertains to the security for a loan being limited to a specific asset or piece of property. Therefore, only the item or property specified in the loan agreement can be pursued by the creditor in the event of default, rather than all of the borrower's assets.
The Ne Varietur term comes from Latin meaning 'not to be changed' and is used in legal documents to indicate that the terms outlined within are to remain unchanged. In the context of a loan, this doctrine would ensure that the borrower's obligation for the debt is limited to the item denoted as collateral, rather than expanding to other assets he might own.