clarify vs explain

clarify

verb
  • To make clear or easily understood; to explain in order to remove doubt or obscurity. 

  • To grow clear or bright; to clear up. 

  • To grow or become clear or transparent; to become free from feculent impurities, as wine or other liquid under clarification. 

  • To make clear or bright by freeing from feculent matter. 

explain

verb
  • To make plain, manifest, or intelligible; to clear of obscurity; to illustrate the meaning of. 

  • To give a valid excuse for past behavior. 

  • To make something plain or intelligible. 

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