cool cat vs imperturbable

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. 

imperturbable

adj
  • Not easily perturbed, upset or excited. 

  • Calm and collected, even under pressure. 

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