What's the "een" in Halloween?
early 15c., "to flood, overflow," from Middle French soronder "to overflow, abound, surpass, dominate," from Late Latin superundare "overflow," from Latin super "over" (see super-) + undare "to flow in waves," from unda "wave" (see water (n.); and cf. abound). Sense of "to shut in on all sides" first recorded 1610s, influenced by figurative meaning in French of "dominate," and by sound association with round. Related: Surrounded; surrounding.