rigorous vs slogging

rigorous

adj
  • Showing, causing, or favoring rigour/rigor; scrupulously accurate or strict; thorough. 

  • Severe; intense. 

slogging

noun
  • An act or an instance of slogging or working laboriously. 

  • A beating or thrashing. 

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