wader vs walking boot

wader

noun
  • A waterproof boot that comes up to the hip, used by fishermen, etc. 

  • One who wades. 

  • A long-legged bird associated with wetland or coastal environments. 

walking boot

noun
  • A hiking boot. 

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