Learn English – What does “arruginated” mean

The Wikipedia entry for Foobar covers this pretty thoroughly (emphasis mine):

The terms foobar, foo, bar, baz and qux are sometimes used as placeholder names (also referred to as metasyntactic variables) in computer programming or computer-related documentation. They have been used to name entities such as variables, functions, and commands whose purpose is unimportant and serve only to demonstrate a concept. The words themselves have no meaning in this usage. Foobar is sometimes used alone; foo, bar, and baz are sometimes used in that order, when multiple entities are needed.

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The origins of the terms are not known with certainty, and several anecdotal theories have been advanced to identify them. Foobar may have derived from the military acronym FUBAR and gained popularity because it is pronounced the same. In this meaning it also can derive from the German word furchtbar, which means awful and terrible and described the circumstances of the Second World War.

FOO is an abbreviation of Forward Observation Officer, a British Army term in use as early as the First World War. The etymology of foo is explored in the Internet Engineering Task Force (IETF) Request for Comments 3092, which notes usage of foo in 1930s cartoons including The Daffy Doc (with Daffy Duck) and comic strips, especially Smokey Stover and Pogo. From there the term migrated into military slang, where it merged with FUBAR. "Bar" as the second term in the series may have developed in electronics, where a digital signal which is considered "on" with a negative or zero-voltage condition is identified with a horizontal bar over the signal label; the notation for an inverted signal foo would then be pronounced "foo bar". Bar may also be read as beyond all repair, which is how it is used in the acronym FUBAR.

The use of foo in hacker and eventually in programming context may have begun in MIT's Tech Model Railroad Club (TMRC). 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."

One book describing the MIT train room describes two buttons by the door: labelled 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.

T.E.D. has a fine answer, just wanted to say it my way. "Proverbial" means "having to do with a proverb", or as T.E.D. says "as heard in a proverb". There are many well-known proverbs in colloquial English. For example, there is one, "people in glass houses shouldn't throw stones", meaning that people in a precarious moral position shouldn't point out the failings of others. English proverbs are generally allegorical, similar to a biblical parable (and some parables, such as the parable of the mustard seed, and other biblical stories like David and Goliath, have remained popular in English even as the culture trends toward the secular). Some are poetic, such as "beer before liquor, never been sicker" (meaning if you start out an evening drinking beer, then progress to hard liquor, you'll have a bad hangover in the morning), and contrary to the connotation of the word "proverb" as imparting ancient wisdom, proverbs are invented all the time ("loose lips sink ships" was coined in World War II, in the months leading up to the D-Day invasion; it was such a big operation with so much of the military and industry involved that the U.S. Government basically asked the entire country to keep whatever they knew or suspected about it secret).

So, a person who talks about "the proverbial man in a glass house" is referring to the proverb in my first example. Where the proverb is known, its imagery can be evoked without recounting it fully.

"Proverbial" can also be used as a synonym for "idiomatic", having a similar meaning but relating instead to idioms. Idioms are popular, somewhat metaphoric sayings regarding common situations; for example:

• Up a creek without a paddle (in trouble with no way of helping yourself)
• Out on a limb (at serious risk for injury to body, reputation, or pride)
• Getting up on the wrong side of the bed (starting the day in a bad mood)
• Getting cold feet (becoming nervous about something one is about to do)
• The pot calling the kettle black (calling someone else out for a flaw you obviously possess yourself)

These sayings can also be referred to "proverbially", even though they're idioms; you may hear of being "up the proverbial creek", which is simply an alternate way of saying "up a creek without a paddle" as the original term has become slightly cliche.