mott vs underbrush

mott

noun
  • A copse or small grove of trees, especially live oak or elm. 

underbrush

noun
  • The small trees and other plants that clutter the floor of a forest. 

verb
  • To clear (an area) of underbrush. 

  • To work among the underbrush. 

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