Halfrican vs mulatto

Halfrican

noun
  • A person who is biracial, with one black parent and one of another race. 

mulatto

noun
  • A person of mixed black and white descent, especially a person with one black and one white parent or two mulatto parents. 

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