Etymology
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buffer (n.1)
"something that absorbs a blow, apparatus for deadening the concussion between a moving body and that against which it strikes," 1835, agent noun from obsolete verb buff "make a dull sound when struck" (mid-16c.), from Old French bufe "a blow, slap, punch" (see buffet (n.2)). Figurative sense of "anything that prevents impact or neutralizes the shock of impact of opposing forces" is from 1858.
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buffer (v.)

"lessen the impact of," 1886, from buffer (n.). Related: Buffered; buffering.

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buffer (n.2)
"one who or that which polishes by buffing," 1854, agent noun from buff (v.).
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bumper (n.)
1670s, "glass filled to the brim;" perhaps from notion of bumping as "large," or from a related sense of "booming" (see bump (v.)). Meaning "anything unusually large" (as in bumper crop) is from 1759, originally slang. Agent-noun meaning "buffer of a car" is from 1839, American English, originally in reference to railway cars; 1901 of automobiles (in phrase bumper-to-bumper, in reference to a hypothetical situation; of actual traffic jams by 1908).
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