folks vs half sister

folks

noun
  • The members of one's immediate family, especially one's parents 

  • People in general; everybody or anybody. 

  • The police. 

  • Late 19th and early 20th century migrants to California from Iowa and other parts of the Midwestern United States. 

half sister

noun
  • A female sibling sharing a single parent. 

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