languish vs plateau

languish

verb
  • To lose strength and become weak; to be in a state of weakness or sickness. 

  • To pine away in longing for something; to have low spirits, especially from lovesickness. 

  • To be neglected; to make little progress, be unsuccessful. 

  • To live in miserable or disheartening conditions. 

plateau

verb
  • (of a varying quantity) To reach a stable level after a period of increase; to level off. 

noun
  • A comparatively stable level after a period of increase. 

  • A notable level of attainment or achievement. 

  • A largely level expanse of land at a high elevation; tableland. 

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