enlist vs unregister

enlist

verb
  • To recruit the aid or membership of others. 

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

  • To secure; to obtain. 

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

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

unregister

verb
  • To undo the process of registration for. 

  • To undo a registration process. 

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