bobbing vs twitching

bobbing

noun

  • The motion of something that bobs. 

twitching

noun

  • The motion of something that twitches. 

  • Compulsive birdwatching by people (twitchers) who travel long distances to see rare species. 

adj

  • That twitches. 

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