Word used often as an identifier by programmers, especially those who write in C/C++ or languages with a similarly brief syntax like Perl. The reason this is so is, to the best of my knowledge, unknown but one might speculate that it is for one or more of the following reasons:

- Because it's not likely to be the name of a variable/function in an included library or a shell command.
- Because you are less likely to overwrite a file that you would rather keep (except maybe one of your own debug files, which is likely to bear a name derived from said word).
- Because it's almost, but not quite, a cuss word.
- Because C programmers hate to use meaningful variable names.

Many coders, however, consider even "foobar" to be too long, opting instead to use each of its halves (i.e. "foo" and "bar") separately. This also gives the programmer an extra identifier to work with, like so:

chomp($foo=`which echo`);
system "$foo Hello World > bar";

The above is, of course, some simple Perl code which finds the location (path) of the "echo" command, storing the result in a variable named "foo." It then proceeds to echo the phrase "Hello World," redirecting the output to a file named bar. This spares the programmer the effort of dreaming up meaningful names (like "$location_of_the_echo_command") for his or her variables.