shibboleth

noun

1. A particular pronunciation or custom that is regarded as distinguishing members of a group from non-members, especially when used as a test.

   “In recent times, the correct treatment of initial h in speech has come to be regarded as a kind of shibboleth of social position.”

   “He also declares that "th" is the veritable English shibboleth. He advises those Germans who cannot pronounce the sound correctly to pronounce it like "d," the symbol which he regularly uses for "th" in his lessons.”

2. A common or longstanding belief, custom, or catchphrase associated with a particular group, especially one with little current meaning or truth.

   “It's about time we abandoned the bourgeois shibboleth that earning money makes you a better person.”

   “The teacher says he must stick largely to the old methods and cling to the old shibboleths or he will naturally get bad results in the examination. Only much practice along the lines the examination is going to follow will insure a [success].”

   “I pose the iconoclastic suggestion that even at this late stage in B.R. dieselisation, rigid standardisation might be a shibboleth.”

   “The truth is that I found success by stumbling off alone in a direction most people thought was a dead end, breaking all the 1990s shibboleths about children’s books in the process.”

   “Yet LBJ was very much a product of the Cold War, believing its shibboleths about communist conquest being irreversible and requiring worldwide containment even when a country, such as Vietnam, that might be falling to the communists did not threaten US national interests.”