insipidity vs shibboleth

insipidity

noun
  • Something that is insipid; an insipid utterance, sight, object, etc. 

  • The condition of being insipid; insipidness. 

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. 

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