undertow vs vortex

undertow

noun
  • A feeling that runs contrary to one's normal one. 

  • A short-range flow of water returning seaward from the waves breaking on the shore. 

verb
  • To pull down by, or as by, an undertow. 

  • To flow or behave as an undertow. 

  • To pull or tow under; drag beneath; pull down. 

vortex

noun
  • Anything that involves constant violent or chaotic activity around some centre. 

  • A whirlwind, whirlpool, or similarly moving matter in the form of a spiral or column. 

  • Anything that inevitably draws surrounding things into its current. 

  • A supposed collection of particles of very subtle matter, endowed with a rapid rotary motion around an axis which was also the axis of a sun or planet; part of a Cartesian theory accounting for the formation of the universe, and the movements of the bodies composing it. 

  • Any of numerous species of small Turbellaria belonging to Vortex and allied genera. 

verb
  • To mix using a vortex mixer 

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