cool cat vs couldn’t care less

cool cat

noun
  • An individual who is at ease and self-assured; one who is calm and composed in interactions with others. 

  • A person who performs or appreciates jazz, especially one whose style of speech and movement is relaxed and rhythmic. 

couldn’t care less

How often have the words cool cat and couldn’t care less occurred in a corpus of books? (source: Google Ngram Viewer )