knack vs skill set

knack

noun
  • Something performed, or to be done, requiring aptness and dexterity. 

  • A petty contrivance; a toy. 

  • A readiness in performance; aptness at doing something. 

verb
  • To speak affectedly. 

skill set

noun
  • The skills needed to accomplish a specified task or perform a given function. 

  • A set of skills. 

How often have the words knack and skill set occurred in a corpus of books? (source: Google Ngram Viewer )