scrub up vs underbrush

scrub up

verb
  • To clean or wash by scrubbing. 

  • To dress up. 

underbrush

verb
  • To clear (an area) of underbrush. 

  • To work among the underbrush. 

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

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