Brownie vs wunderkind

Brownie

noun
  • A junior Girl Guide. 

  • A junior Girl Scout. 

name
  • A nickname of the surname Brown. 

wunderkind

noun
  • A child prodigy; a phenom. 

  • A highly talented or gifted individual, especially one who is successful at a young age. 

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