formication vs tickling

formication

noun
  • An abnormal skin sensation similar to that of insects crawling over or within the skin; a tactile hallucination involving such a sensation. A common side-effect of substance abuse, it can also be experienced with high fever, menopause, skin cancer, diabetic neuropathy, or herpes zoster. 

tickling

noun
  • A sensation that tickles. 

  • The act by which someone is tickled. 

adj
  • That tickles 

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