chaparral vs undergrowth

chaparral

noun
  • The foliage of creosote bush, Larrea divaricata, when used as a medicinal herb. 

  • A region of shrubs, typically dry in the summer and rainy in the winter. The coast of the Mediterranean is such a region. 

undergrowth

noun
  • The plants in a forest which only reach a relatively low height (such as shrubs and bushes). 

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