off the deep end vs quicksilver

off the deep end

adj

  • Crazy, erratic, or irrational. 

  • Extremely angry. 

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 off the deep end and quicksilver occurred in a corpus of books? (source: Google Ngram Viewer )