excogitate vs understand

excogitate

verb
  • To think over something carefully; to consider fully; cogitate. 

  • To reach as a conclusion through reason or careful thought. 

understand

verb
  • To grasp a concept fully in one's mind, especially (of words, statements, art, etc.) to be aware of the meaning of and (of people) to be aware of the intent of. 

  • To believe, to think one grasps sufficiently despite potentially incomplete knowledge. 

  • To stand underneath, to support. 

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