titillate vs vellicate

titillate

verb
  • To stimulate or excite sensually 

vellicate

verb
  • To touch (a body part) lightly so as to excite the surface nerves and cause uneasiness, laughter, or spasmodic movements. 

  • To twitch or move convulsively. 

  • To tickle, provoking twitching and laughter. 

  • To criticize in a somewhat irritating way; to carp at. 

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