caste vs ethnos

caste

noun
  • A separate and fixed order or class of persons in society who chiefly associate with each other. 

  • Hyponyms: Brahmin, Kshatriya, Shudra, Vaishya, varna 

  • Any of the hereditary social classes and subclasses of South Asian societies. 

  • A class of polymorphous eusocial insects of a particular size and function within a colony. 

ethnos

noun
  • An ethnic group, or a people who have a common national or cultural tradition 

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