shibboleth vs tag line

shibboleth

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

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

tag line

noun
  • Synonym of dialogue tag 

How often have the words shibboleth and tag line occurred in a corpus of books? (source: Google Ngram Viewer )