Ask a programmer for an example, and the imaginary parts will probably be called foo, bar, and, when a third is needed, baz. Programmers call these stand-ins metasyntactic variables: names that point at nothing real. By 2001, about 212 RFCs (Requests for Comments), the Internet's technical documents, had used foo, bar, or foobar without a word of explanation. On April 1 of that year, RFC 3092, “Etymology of ‘Foo,’” set out to explain them for newcomers, especially readers whose first language was not English.
Its authors were Donald Eastlake 3rd of Motorola, a lead author of the security extensions for the Domain Name System, the Internet's address book; Carl-Uno Manros of Xerox, who had chaired the effort that produced the Internet Printing Protocol; and Eric S. Raymond, a co-founder of the Open Source Initiative who kept the Jargon File, hacker culture's dictionary of its own slang. Their trail began with Smokey Stover, cartoonist Bill Holman's surreal 1930s comic strip about a fireman, which scattered FOO across license plates and slogans such as “He who foos last foos best” and “Where there's foo, there's fire.” Holman said he found the word on the bottom of a Chinese figurine. The RFC's authors thought that plausible: Chinese statuettes often carry inscriptions meant to protect and bless, and the word may have been fu, which can mean good fortune or happiness. Foo fever produced more than 500 Foo Clubs, and in a 1938 Warner Bros. cartoon Daffy Duck held up a sign reading “SILENCE IS FOO!”
Then the word went to war. In 1944 and 1945, radar operators called mysterious blips “foo fighters,” and British troops scrawled “FOO was here” the way Americans wrote “Kilroy was here.” The Army's unprintable acronym FUBAR - "F'd Up Beyond All Recognition", or more politely, “fouled up beyond all repair” — tangled with foo to make foobar, though the RFC's authors suspected foobar came first. By 1959, the Massachusetts Institute of Technology's Tech Model Railroad Club, the student club where hacker culture took shape, had a dictionary entry for Foo; its online version playfully borrows Om mani padme hum, a revered Tibetan Buddhist mantra of compassion, calling Foo “the sacred syllable (FOO MANI PADME HUM).” A Placeholder is meant to stand in quietly for something else, and foo did the job so well that nobody can say for certain where it came from.
