folk vs half sister

folk

noun
  • One’s relatives, especially one’s parents. 

  • People in general. 

  • The inhabitants of a region, especially the native inhabitants. 

  • A particular group of people. 

adj
  • Of or pertaining to common people as opposed to ruling classes or elites. 

  • Of or pertaining to the inhabitants of a land, their culture, tradition, or history. 

  • Of or related to local building materials and styles. 

  • Believed or transmitted by the common people; not academically correct or rigorous. 

half sister

noun
  • A female sibling sharing a single parent. 

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