shibboleth

noun2

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