"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)). The figurative sense of "anything that prevents impact or neutralizes the shock of impact of opposing forces" is from 1858.
"computer operating system using a disk storage device," 1967, acronym of disk operating system.
registered trademark (U.S. Patent Office, 1941) of a type of refrigerator; used generically for "cold storage" since 1949.