shrub vs undergrowth

shrub

noun
  • A woody plant smaller than a tree, and usually with several stems from the same base. 

  • A word mispronounced by replacing some consonant sounds with others of a similar place of articulation due to interference from one's knowledge of an indigenous Kenyan language. 

  • A liquor composed of vegetable acid, fruit juice (especially lemon), sugar, sometimes vinegar, and a small amount of spirit as a preservative. Modern shrub is usually non-alcoholic, but in earlier times it was often mixed with a substantial amount of spirit such as brandy or rum, thus making it a liqueur. 

verb
  • To mispronounce a word by replacing some consonant sounds with others of a similar place of articulation due to interference from one's knowledge of an indigenous Kenyan language. 

undergrowth

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

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