aunt-in-law vs first cousin once removed

aunt-in-law

noun

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

  • The aunt of one's husband. 

  • The aunt of one's wife. 

first cousin once removed

noun

  • A parent's first cousin. 

  • A first cousin's child. 

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