I came across the word ’shibboleth’ recently and thought it sounded cool, and decided to look up what it meant. The origin of its usage is in the Bible:

The story behind the word is recorded in the biblical Book of Judges. The word shibboleth in ancient Hebrew dialects meant ‘ear of grain’ (or, some say, ’stream’). Some groups pronounced it with a sh sound, but speakers of related dialects pronounced it with an s.

In the story, two Semitic tribes, the Ephraimites and the Gileadites, have a great battle. The Gileadites defeat the Ephraimites, and set up a blockade to catch the fleeing Ephraimites. The sentries asked each person to say the word shibboleth. The Ephraimites, who had no sh sound in their language, pronounced the word with an s and were thereby unmasked as the enemy and slaughtered.