aunt-in-law vs kinswoman

aunt-in-law

noun

  • The aunt of one's wife. 

  • The aunt of one's husband. 

  • The wife of one's uncle or aunt (parent's sibling). 

kinswoman

noun

  • A female relative. 

How often have the words aunt-in-law and kinswoman occurred in a corpus of books? (source: Google Ngram Viewer )