endure vs keep on

endure

verb
  • To continue or carry on, despite obstacles or hardships; to persist. 

  • To tolerate or put up with something unpleasant. 

  • To remain firm, as under trial or suffering; to suffer patiently or without yielding; to bear up under adversity; to hold out. 

  • To last. 

  • To suffer patiently. 

keep on

verb
  • To persist or continue. 

  • To cause or allow to remain in the on or open position. 

  • To cause or allow to remain in an existing position. 

  • To persist in talking about a subject to the annoyance of the listener. 

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