Madame L first heard of the the word "shibboleth" in Sunday School, years ago. It was a kind of password, a trick to distinguish the Gileadites, who had the "sh" sound in their Hebrew dialect, from the Ephraimites, who did not have that sound.
So, in around 1370 to 1070 BC, as Ephraimites warriors were trying to cross the Jordan River to get back to their homes after a battle they'd lost to the Gileadites, the winning tribe demanded that the losers say "shibboleth." If they said "sibboleth" instead, they gave themselves away and were killed as Ephraimites (Judges 12).
What are some modern-day shibboleths? Madame L knows an American lady married to a man whose first language does not have the "p" sound we have in English. The wife always thought it was funny when her husband would order at a fast-food drive through, as he said, in almost unaccented English, "I'll have a cheeseburger and fries and a Bebsi." (Fortunately, nowadays our shibboleths don't usually result in a death sentence!)
Forensic linguists have used similar linguistic clues to find criminals. Written language, certain expressions common only in a certain area, speech patterns, and accents all give clues as to who we are.
But what does the word "shibboleth" mean in the original Hebrew? According to Wikipedia, it means the part of a plant that actually contains the grain, such as an ear of corn or a stalk of grain; it can also mean "stream" or "torrent."
The Wikipedia article gives some more fascinating details about historical and current usage of the word and the idea of the shibboleth.