call up vs enroll

call up

verb
  • To summon (someone) to report for military service. 

  • To select e.g. to a sports squad. 

  • To retrieve from personal or computer memory. 

  • To call on the telephone. 

noun
  • An order to report for military service. 

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 

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