mildew vs pejorate

mildew

verb
  • To become tainted with mildew. 

  • To taint with mildew. 

noun
  • A growth of minute powdery or webby fungi, whitish or of different colors, found on various diseased or decaying substances. 

pejorate

verb
  • To make or become worse; to deteriorate or to worsen. 

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