A Borrower takes and uses something that belongs to someone else, with the intention of returning it. You have an impatient borrower and a patient lender. It is the trade off between patience and impatience, which is going to decide the rate of interest.
A loan entails the redistribution of financial assets over time, between the lender and the borrower. Collateral may be used to make sure the borrower keeps his promise. The borrowing may be secured by collateral, or it may be unsecured in which case there are no assets guaranteeing pay back.
As investors use the term the borrower is the person who initially receives an amount of money, called the principal, from the lender, and is obligated to, pay back, all of the funds, plus interest and fees, to the lender by a specified time.
From to lend, be surety for, pledge, to hide, protect. Apparently on the notion of collateral deposited as security for something borrowed.  Bury, to raise a mound, hide, bury, to shelter, protection, shelter, to save, preserve.