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Tim Carmichael wrote:

It's one of the phrases that has crept into common use.

The use of foo in a programming context is generally credited to the Tech Model Railroad Club (TMRC) of MIT from circa 1960.[1] In the complex model system, there were scram switches located at numerous places around the room that could be thrown if something undesirable was about to occur, such as a train going full-bore at an obstruction. Another feature of the system was a digital clock on the dispatch board. When someone hit a scram switch, the clock stopped and the display was replaced with the word "FOO"; at TMRC the scram switches are, therefore, called "Foo switches". Because of this, an entry in the 1959 Dictionary of the TMRC Language went something like this: "FOO: The first syllable of the misquoted sacred chant phrase 'foo mane padme hum.' Our first obligation is to keep the foo counters turning."[5] One book[which?] describing the MIT train room describes two buttons by the door: labeled "foo" and "bar". These were general purpose buttons and were often re-purposed for whatever fun idea the MIT hackers had at the time, hence the adoption of foo and bar as general purpose variable names.