kaffir vs nig-nog

kaffir

noun
  • A black person. 

  • South African mining shares 

  • A member of the Nguni people of southern Africa, especially a Xhosa. 

  • A language spoken by the Nguni peoples of southern Africa, especially Xhosa. 

  • In Islamic contexts, a non-Muslim. 

nig-nog

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

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

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