means To give money back to someone, typically because goods were returned or a service wasn't delivered as promised; also the sum of money so returned.

from From the Latin refundere, literally 'to pour back' — re- ('back') plus fundere ('to pour'), the same fundere that gives us 'fuse' and 'foundry.' It entered English through Old French in the late medieval period, first meaning to pour or give back generally, and later narrowing to the modern sense of returning money.