1. interj. Term of disgust. 2. [very common] Used very generally as a sample name for absolutely anything, esp. programs and files (esp. scratch files). 3. First on the standard list of metasyntactic variables used in syntax examples. See also bar, baz, qux, quux, corge, grault, garply, waldo, fred, plugh, xyzzy, thud.
When `foo' is used in connection with `bar' it has generally traced to the WWII-era Army slang acronym FUBAR (`F@#&!* Up Beyond All Repair'), later modified to foobar. Early versions of the Jargon File interpreted this change as a post-war bowdlerization, but it it now seems more likely that FUBAR was itself a derivative of `foo' perhaps influenced by German `furchtbar' (terrible) - `foobar' may actually have been the original form.
For, it seems, the word `foo' itself had an immediate prewar history in comic strips and cartoons. The earliest documented uses were in the "Smokey Stover" comic strip published from about 1930 to about 1952. Bill Holman, the author of the strip, filled it with odd jokes and personal contrivances, including other nonsense phrases such as "Notary Sojac" and "1506 nix nix". The word "foo" frequently appeared on license plates of cars, in nonsense sayings in the background of some frames (such as "He who foos last foos best" or "Many smoke but foo men chew"), and Holman had Smokey say "Where there's foo, there's fire".
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