cover story vs grounds

cover story

noun
  • A fictitious account that is intended to hide one's real motive. 

  • A story included in a publication that is highlighted on the front cover. 

grounds

noun
  • Basis or justification for something. 

  • The sediment at the bottom of a liquid, or from which a liquid has been filtered. 

  • The collective land areas that compose a larger area. 

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