struggle vs take on

struggle

verb
  • To strive, to labour in difficulty, to fight (for or against), to contend. 

  • To strive, or to make efforts, with a twisting, or with contortions of the body. 

noun
  • A contortion of the body in an attempt to escape or to perform a difficult task. 

  • Strife, contention, great effort. 

take on

verb
  • To attempt to fight, compete with, or engage with. 

  • To assume or take responsibility for. 

  • To (attempt to) dribble round (an opposition player). 

  • To catch on, do well; to become popular. 

  • To obtain the services of (a person) in exchange for remuneration; to give someone a job. 

  • To begin to have or exhibit. 

  • To acquire, bring in, or introduce. 

  • To grieve or be concerned (about something or someone). 

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