eddy vs undercurrent

eddy

noun
  • A current of air or water running back, or in an opposite direction to the main current. 

  • A circular current; a whirlpool. 

  • A marijuana edible. 

verb
  • To form an eddy; to move in, or as if in, an eddy; to move in a circle. 

undercurrent

noun
  • A current of water which flows under the surface, and often in a different direction from surface currents. 

  • A tendency of feeling or opinion that is concealed rather than exposed. 

verb
  • To flow under some surface. 

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