What's the "een" in Halloween?
late 14c., "to overflow," from Old French redonder "overflow, abound, be in profusion" (12c.), from Latin redundare "to overflow" (see redundant). Meaning "to flow or go back" (to a place or person) is from late 14c.; hence "to rebound" (c.1500), and "to contribute to" (the credit, honor, etc.), early 15c. Related: Redounded; redounding.