fee vs take on

fee

verb
  • To reward for services performed, or to be performed; to recompense; to hire or keep in hire; hence, to bribe. 

noun
  • A right to the use of a superior's land as a stipend for certain services to be performed, typically military service. 

  • An additional monetary payment charged for a service or good that is minor compared to the underlying cost. 

  • Synonym of fief: the land so held. 

  • An inheritable estate in land, whether absolute and without limitation to potential heirs (fee simple) or with limitations to particular kinds of heirs (fee tail). 

  • An inheritable estate in land held of a feudal lord on condition of performance of certain services, typically military service. 

take on

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

  • To assume or take responsibility for. 

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

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

  • To begin to have or exhibit. 

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

  • To acquire, bring in, or introduce. 

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

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