qualify vs thicken

qualify

verb
  • To give individual quality to; to modulate; to vary; to regulate. 

  • To certify or license someone for something. 

  • To throw and catch each object at least twice. 

  • To compete successfully in some stage of a competition and become eligible for the next stage. 

  • To make someone, or to become competent or eligible for some position or task. 

  • To modify, limit, restrict or moderate something; especially to add conditions or requirements for an assertion to be true. 

  • To describe or characterize something by listing its qualities. 

noun
  • An instance of throwing and catching each prop at least twice. 

thicken

verb
  • To strengthen; to confirm. 

  • To become thicker (in the sense of wider). 

  • To become thicker (in the sense of more viscous). 

  • To make thicker (in the sense of more viscous). 

  • To make thicker (in the sense of wider). 

  • To make more frequent. 

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