A shibboleth is a cultural tradition or custom that distinguishes a group of people from another. Just looking at the term, it seems apparent that it comes from Hebrew, and if you made that conclusion, you'd be right - it traces to a word sounding like shibbolet and meaning "ear of corn". The story behind this takes us back to the Book of Judges in the Old Testament, in which the Gileadites needed to figure out who the Ephraimites were, so they asked everyone to pronounce shibboleth. Since the Ephraimites weren't able to pronounce the sh sound, the Gileadites were able to weed them out from their own and slaughter them. After that the word evolved to refer to societal markers in general. Shibbolet comes from the Proto-Semitic root sh-b-l, which probably could also mean "stalk of grain".
Adam Aleksic, a rising sophomore studying linguistics and government at Harvard University, has been described as the internet's sixth most famous etymologist. He also has disturbing interests in politics, vexillology, geography, board games, conlanging, and law.