enroll vs obtain

enroll

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

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

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

obtain

verb
  • To get hold of; to gain possession of, to procure; to acquire, in any way. 

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