flickering vs smouldering

flickering

noun
  • A short, uncertain burst. 

adj
  • shining unsteadily or varying rapidly in brightness (referring to a light or a source of light) 

smouldering

noun
  • The act by which something smoulders; residual heat. 

adj
  • Burning slowly, producing smoke but no flame. 

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