A shibboleth is any custom or tradition, usually a choice of phrasing or even a single word, that distinguishes one group of people from another. Shibboleths have been used throughout history in many societies as passwords, simple ways of self-identification, signaling loyalty and affinity, maintaining traditional segregation, or protecting from real or perceived threats.
Bibliography
“Shibboleth.” 2023. Wikipedia, July. https://en.wikipedia.org/w/index.php?title=Shibboleth&oldid=1166816137.