acid test vs credence

acid test

noun
  • A rigorous test or appraisal of the quality or worth of something. 

  • In the 1960s, a party based around the use and advocacy of the psychedelic drug LSD ("acid"). 

credence

noun
  • Credential or supporting material for a person or claim. 

  • Acceptance of a belief or claim as true, especially on the basis of evidence. 

  • A small table or credenza used in certain Christian religious services. 

  • A cupboard, sideboard, or cabinet, particularly one intended for the display of rich vessels or plate on open shelves. 

  • A subjective probability estimate of a belief or claim. 

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