disenroll vs enroll

disenroll

verb
  • To cancel enrolment of; to remove from a list. 

  • To eject (a member) from a tribe. 

enroll

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

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

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

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