erratic vs quicksilver

erratic

adj
  • Unsteady, random; prone to unexpected changes; not consistent. 

  • Deviating from normal opinions or actions; eccentric; odd. 

noun
  • A rock moved from one location to another, usually by a glacier. 

  • Anything that has erratic characteristics. 

quicksilver

adj
  • Unpredictable, erratic or fickle; mercurial. 

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. 

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