prolong vs tallen

prolong

verb
  • To become longer; lengthen. 

  • To lengthen in time; to extend the duration of 

  • To put off to a distant time; to postpone. 

  • To extend in space or length. 

tallen

verb
  • To become tall or taller 

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