saccade vs vellication

saccade

noun
  • A sudden jerking movement. 

  • The sounding of two violin strings together by using a sudden strong pressure of the bow. 

  • A rapid jerky movement of the eye (voluntary or involuntary) from one focus to another. 

  • The act of checking a horse quickly with a single strong pull of the reins. 

verb
  • To make a rapid jerking movement to focus elsewhere. 

vellication

noun
  • A spasm or twitch. 

  • An instance of tickling or minor irritation. 

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