affine vs co-father-in-law

affine

noun
  • A relative by marriage. 

verb
  • To refine. 

adj
  • Of or pertaining to a function expressible as f(⃑x)=A⃑x+⃑b (where A is a linear transformation and ⃑b is a constant), which, regarded as a transformation, maps parallel lines to parallel lines and finite points to finite points. 

  • Assigning finite values to finite quantities. 

  • Of two materials, having mutual affinity. 

co-father-in-law

noun
  • The father of one's son- or daughter-in-law; that is, the father-in-law of one's child, or, the father of one spouse in relation to the father of the other spouse; either of two or more men whose children marry each other, such as the father of a bride vis-à-vis the father of the groom. 

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