shibboleth

shibboleth\SHIB-uh-lith; -leth\ , noun:
1. A peculiarity of pronunciation, behavior, mode of dress, etc., that distinguishes a particular group of persons.
2. A slogan; a catchword.
3. A common saying or belief with little current meaning or truth.

Origin:
Shibboleth is from Hebrew shibboleth, "stream, flood," from the use of this word in the Bible (Judges 12:4-6) as a test to distinguish Gileadites from Ephraimites, who could not say 'sh' but only 's' as in 'sibboleth'.

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I wasn't familiar with this word, but when I read the origin of shibboleth, I immediately thought of something I read in some WWII book or story about how sentries, when wanting to further verify the identity of someone challenged and who knew the password, used American trivia that every US soldier would know but an enemy most likely would not. I also remember reading something very similar in regards to the Pacific theater part of the war and found a source for that at Wiki.

From Wiki:

Shibboleths have been used by different subcultures throughout the world at different times. Regional differences, level of expertise and computer coding techniques are several forms that shibboleths have taken. For example, during the Battle of the Bulge, American soldiers used knowledge of baseball to determine if others were fellow Americans or if they were German infiltrators in American uniform. The Dutch famously used the name of the port town Scheveningen as a shibboleth to tell Germans from the Dutch. Some shibboleths are jokes.

During World War II, some United States soldiers in the Pacific theater used the word "lollapalooza" as a shibboleth to verbally test people who were hiding and unidentified, on the premise that Japanese people often pronounce the letter L as R, and that the word is an American colloquialism that even a foreign person fairly well-versed in American English would probably mispronounce and/or be unfamiliar with. In George Stimpson's A Book about a Thousand Things, the author notes that, in the war, Japanese spies would often approach checkpoints posing as American or Filipino military personnel. A shibboleth such as "lollapalooza" would be used by the sentry, who, if the first two syllables come back as rorra, would "open fire without waiting to hear the remainder".