Lets someone use something that belongs to them with the intention of getting it back. Lending gives the borrower greater flexibility in dealing with temporary fluctuations in cash flow. One who lends. 
Lending and borrowing are basically about smoothing out the flow of cash into and out of a persons budget. A lender receives interest on the principal that he lends, and the borrower pays back more than they receive. The lender gets paid for giving up the use of the money for a time, and must also be compensated for the risk of delayed or non-repayment of the principal by the borrower.
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.