bumper Look up bumper at Dictionary.com
1670s, "glass filled to the brim;" perhaps from notion of bumping as "large," or from a related sense of "booming" (see bump). Meaning "anything unusually large" is from 1759, slang. Meaning "buffer of a car" is from 1839, Amer.Eng., originally in reference to railway cars; 1926 of automobiles.