quicksilver vs yo-yo

quicksilver

verb
  • To overlay with quicksilver. 

  • To treat with quicksilver. 

noun
  • The metal mercury. 

  • An amalgam of mercury and tin applied to the backs of mirrors, quicksilvering. 

adj
  • Unpredictable, erratic or fickle; mercurial. 

yo-yo

verb
  • To vacillate; to move up and down. 

noun
  • A toy consisting of a spheroidal or cylindrical spindle having a circular groove in which string is wound; it is used by holding the string in the fingers and reeling the spindle up and down by movements of the wrist. 

  • A cloth rosette formed by gathering the outside edge of a circle of fabric in toward the centre using a running stitch. 

  • Someone who vacillates. 

  • A dogfighting maneuver involving the attacker temporarily exchanging altitude for airspeed, or vice versa, in order to rapidly catch up with the defender or to prevent an overshoot. 

  • A volatile market that moves up and down. 

  • A foolish, annoying or incompetent person. 

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