immortalise vs keep up

immortalise

verb
  • To give unending life to, to make immortal. 

  • To make eternally famous. 

keep up

verb
  • To maintain; to preserve; to prevent from deteriorating. 

  • To continue with (work, etc). 

  • To stay even or ahead. 

  • To ensure that one remains well-informed about something. 

  • To prevent someone from going to bed or to sleep 

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