Life is easy to chronicle, but bewildering to practice, and we welcome "nerves" or any other shibboleth
that will cloak our personal desire.
E.M. Forster -- A Room With A View
a custom or belief that identifies one as a member of a group of people and which others believe to be foolish or outdated
More rarely, shibboleth can reference a language usage or pronunciation, or other custom that identifies one as belonging to a group without a negative inference.