As long as I can recall, my dad has referred to BMW's as "Bimmers," and over time I've also heard people call them "Beamers." So where does it stem from and which is "proper"?
In the early part of the 20th century, The British motorcycle company BSA started racing motorcycles that used BMW motors and parts. Adapted from the early-20th century British pronunciation of BSA - "Beesuh" (as "beeser" or "beezer"). The term "bimmer" started as an acronym for the abbreviation "BMW."
Afficianados make the distinction that "Bimmer" (rhymes with "trimmer") is referring to the automobile BMW, while the American-butchered "Beamer" (rhymes with "screamer") refers to the motorcycle BMW.
The Canadian Globe and Mail prefers "Bimmer" and calls "Beemer" a "yuppie abomination,"while the Tacoma News Tribune says it is a distinction made by "auto snobs."
An editor of Business Week was satisfied in 2003 that the question was resolved in favor of "Bimmer"by noting that a Google search yielded 10 times as many hits compared to "Beemer"