late 14c., redounden, "to overflow, flow abundantly; abound, multiply, increase" (senses now obsolete), also "to flow or go back" (to a place or person), "be sent, rolled, or driven back," from Old French redonder "overflow, abound, be in profusion" (12c.), from Latin redundare "to overflow" (see redundant). Hence "to contribute, have effect" (to the credit, honor, etc.), early 15c. Related: Redounded; redounding.