A shibboleth is any custom or tradition, particularly a speech pattern, that distinguishes one group of people (an ingroup) from others (outgroups). Shibboleths have been used throughout history in many societies as passwords, simple ways of self-identification, signaling loyalty and affinity, maintaining traditional segregation or keeping out perceived threats.
The general name for this type of thing is “Shibboleth,” after a city whose name was used that way in the Bible. Shibboleths are interesting to learn about, partly because it’s deep-cover spycraft, and partly because they words used are always whackadoodle nonsense.
In WWII, the Dutch would identify German spies by how they pronounced “Scheveningen,” a district in the Hague. The Germans pronounced the first syllable as something like the English word “chef,” while the Dutch version has a guttural “skhef” sound.