refund
v.
"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.
n.
"a return of money paid," 1782, from refund, v..
〔李〕[re-=back回；fund=to pour灌注→“to pour back or flow back倒灌或倒流回去”→] v. give or pay back归还；偿还