half-breed vs mulatto

half-breed

noun
  • A person of mixed racial parentage or ancestry, especially one of mixed white and American Indian parentage (metis, métis, Metis, Métis; mestizo). 

  • A hybrid animal or plant. 

adj
  • Having dual heritage; having mixed racial parentage or ancestry. 

  • Hybridized; having one purebred parent; descended from parents of different breeds or with different traits. 

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 half-breed and mulatto occurred in a corpus of books? (source: Google Ngram Viewer )