mulling vs ratiocination

mulling

noun
  • The act of one who mulls or thinks over something. 

ratiocination

noun
  • Reasoning, conscious deliberate inference; the activity or process of reasoning. 

  • Thought or reasoning that is exact, valid and rational. 

  • A proposition arrived at by such thought. 

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