Ode to Foobar

Every computer science student encounters foobar sooner or later in their education. Usually without any preamble or explanation of convention, foobar or foo is written on blackboards, used in examples, and appears in textbooks. Probably as something like this, from K-State’s Introduction to Python:

1def foo():
2    print("eye")
3
4
5def bar():
6    print("to")
7
8
9foo()
10bar()
11foo()

And the thing is, like so many other things in higher education, nobody ever explains what foobar means. Rarer still, nobody thinks to ask. Students just seem to acquire it implicitly, or just accept it as a fact of the foo-niverse.

I heard foobar for the first time when I was auditing CSCI S-7 at Harvard Summer School taught by Henry Leitner. In a class where he was introducing the concept of an algorithm, he handed a student in the front row a dictionary and asked him to search for foobar. Of course, he didn’t find it, and it prompted a lesson on approaches to search. I wrote down foobar?? in the corner of my notes, and didn’t think about it much until I sat down to write this blog post.

But I’ve had an epiphany and I need to share with you what’s been revealed to me. I want to make something absolutely, explicitly clear, without any hint of ambig-foo-ity. I love foobar. It’s a goofy, sweet word. It could be a fat golden retriever’s name (with potential nicknames Fooby or Boofy). It could be a muppet. It could be a beloved family nickname, perhaps given by a toddler-age sibling who couldn’t pronounce something like Robert or Theodore quite correctly. “Oh, my folks call me Foobar. It’s a long story.”

What I have gathered for you here today is the ultimate celebration of foobar and its meronym, foo. I have chosen to foo-cus on (rough) homophones rather than a strict adherence to spelling or direct relation to CS. Consequently, I have excluded foo [ˈɸɔː] (“in, inside”) in Murui Huitoto, phở [fəː˧˩] in Vietnamese, and English words like fool, foosball, or futon. Because Fu/Foo is a very common last name, I have only included a few famous Fu/Foo/Fous, especially those whose work I admire.

So here’s some foo-d for thought, and foo-sic for the soul. For the optimal experience, listen to Canon in Foo while you browse.

All of the other nonsense placeholder conventions (“metasyntactic variables”) don’t seem to have the same je ne sais foo, if you know what I mean. Here’s a short list of examples: baz, qux, xyzzy, corge, grault, garply, waldo, fred, plugh, thud, dummy. To my ear, these all sound kind of dull or ungraceful, while foobar seems to roll off the tongue.

Foobar has a tantalizing mystery about it. Nobody knows exactly where it began. The earliest foo appeared in the Smokey Stover comics in the 1930s. Then WWII gave us FUBAR, which I won’t spell out for you here. And from 1959 on, it entered computing and hacker culture, the apotheotic example coming from the Tech Model Railroad Club’s dictionary at MIT, which calls FOO “the sacred syllable” and declares, “Our first obligation is to keep the Foo Counters turning.” For a more detailed etymology of foobar, see RFC 3092, published on April 1st, 2001 (foo-thousand-one).

The real reason we can’t seem to identify the true ur-foo is that foo is ubiquitous across languages. The consonant /f/ occurs in about 44% of languages, and /u/ in about 88% (PHOIBLE). If a language happens to have both, it’s a relatively unremarkable syllable. English, Scots, French, Mandarin, and Spanish all have some variation of /fu/. In Mandarin, with respect to tone, fu can mean husband/man (夫 fū), woman/wife (妇 fù), skin (肤 fū), good fortune (福 fú), clothing (服 fú), mansion/government office (府 fǔ), rotten (腐 fǔ), rich (富 fù), to float (浮 fú), to serve (服 fú), to carry/to lose (负 fù), to return (复 fù).

It was just the time that someone combined it with bar in English that we were really cooking with fire. I’ll show you: let’s talk about the foo-netics of foobar. I’m going to focus specifically on General American English, because that’s the dialect I’m most familiar with.

Foobar is pronounced [ˈfuˌbɑɹ], with primary stress on the first syllable and a secondary stress on the second. This is common in compound words like blackbird, classmate, or hotdog. Neither of the vowels reduce (to something like [ˈfubɚ], weird), and therefore it really does behave like the fuse of foo and bar. Both starting consonants /f/ and /b/ are labial, and the vowel sounds transition nicely from high back rounded [u] to low back unrounded [ɑ], almost like it was always meant to be said. Foobar…

Additionally, the graphetics of foobar are incredibly pleasant. It looks like it could be a naturally occurring word. Unlike my previous examples of xyzzy or qux, it has a shape shared by many common English words. It goes: consonant, vowel cluster, consonant, vowel, consonant. There’s no weird clusters, no end-of-the-alphabet oddballs like x, y, or z. Could phoobar have been as famous? Could fuhbahr?

I think these linguistic properties contribute greatly to the memetic signi-foo-cance of foobar, especially in nerd world. It’s become a kind of cultural touchstone, almost an easter egg. And it’s kind of beautiful as well, because as a junk variable, foobar refers to nothing, but to us, foobar means everything.

Every time you define a variable as foo, know that you are participating in a decades-old practice with a rich linguistic and cultural history. If you are new to Computer Science, I hope that this knowledge guides you on your journey. If you are an old-timer, take a moment to tell your juniors a bit about the history of foobar. It’s not a word in the Merriam-Webster dictionary (the exact book Henry Leitner tore in half to explain binary search), but it’s written 4 million times on GitHub, in the archives of Usenet, and across all of our hearts.

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blog post over, only foos below