nig-nog vs shitskin

nig-nog

noun
  • A person of color, especially, a black person. 

  • A foolish person; hence, a raw and unskilled recruit. 

shitskin

noun
  • A person with dark-coloured skin. 

How often have the words nig-nog and shitskin occurred in a corpus of books? (source: Google Ngram Viewer )