imperturbability vs self-confidence

imperturbability

noun
  • A state of calm, unruffled self-assurance; aplomb, composure. 

self-confidence

noun
  • The state of being self-confident 

  • A measure of one's belief in one's own abilities 

How often have the words imperturbability and self-confidence occurred in a corpus of books? (source: Google Ngram Viewer )