refund (v.) Look up refund at
"to give back, restore," early 15c. (earlier "to pour back," late 14c.), from Old French refunder "restore" and directly from Latin refundere "give back, restore, return," literally "pour back, flow back," from re- "back" (see re-) + fundere "to pour" (see found (v.2)). Specifically of money from 1550s. Related: Refunded; refunding.
refund (n.) Look up refund at
"a return of money paid," 1782, from refund (v.).