downlink vs enroll

downlink

noun
  • Transmission of data from a network, usually wireless, to the user. 

  • The transmission of a signal from a satellite to a receiving station on earth; or the means of this transmission. 

verb
  • To transmit a signal from a satellite to a terrestrial receiving station. 

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 downlink and enroll occurred in a corpus of books? (source: Google Ngram Viewer )