Shibboleth

A shibboleth ( ; Biblical Hebrew: שִׁבֹּלֶת, romanized: šībbōleṯ) is any custom or tradition, usually a choice of phrasing or single word, that distinguishes one group of people from another. Shibboleths have been used throughout history in many societies as passwords, ways of self-identification, signals of loyalty and affinity, ways of maintaining traditional segregation, or protection from real or perceived threats.