enlist vs enroll

enlist

verb
  • To enter on a list; to enroll; to register. 

  • To recruit the aid or membership of others. 

  • To secure; to obtain. 

  • To voluntarily join a cause or organization, especially military service. 

noun
  • One who is enlisted, usually in a military service. 

enroll

verb
  • To enter (a name, etc.) in a register, roll or list 

  • To enlist oneself (in something) or become a member (of something) 

  • To enlist (someone) or make (someone) a member of 

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