shibboleth

A word or pronunciation that distinguishes people of one group or class from those of another.

A word or phrase identified with a particular group or cause; a catchword.

A commonplace saying or idea.

A custom or practice that betrays one as an outsider.

A Hebrew word, meaning ‘ear of corn’ or ‘stream,’ used by Jephthah, one of the judges of Israel, as a test-word by which to distinguish the fleeing Ephraimites (who could not pronounce the sh in shibboleth) from his own men, the Gileadites (Judges xii. 4–6); hence, a test-word, or the watchword or pet phrase of a party, sect, or school.

A word which was made the criterion by which to distinguish the Ephraimites from the Gileadites. The Ephraimites, not being able to pronounce sh, called the word sibboleth. See Judges xii.

Also used in an extended sense.

Hence, the criterion, test, or watchword of a party; a party cry or pet phrase.

A word, especially seen as a test, to distinguish someone as belonging to a particular nation, class, profession etc.