foo bar is very often used in computer programming, used to declare a (temporary) variable.
Most probably, "foo" and "bar" came from "foobar," which in turn had its origins in the military slang acronym FUBAR. The most common rendition is "Fucked Up Beyond All Recognition"
Suppose we have a function named bar and a variable foo. To call the function we use foo bar.
by Dave March 29, 2006
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A slang term meaning "fucked up beyond all recognition." The saying was used primarilly in programing and originated as fubar, but for political correctness it was changed to foo bar.

Foo and bar also often represent variables.
Dude that thing is foo bar!
by ted_yc April 23, 2006
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A place that Mr. T wont hang out.
$foo=1; echo "that is $foo foo that i pity!";

$bar="stay out of that foo bar sucka!";
by NotYourFoo July 18, 2010
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