half-uncle vs uncle-in-law

half-uncle

noun

  • A half brother-in-law of one's parent. 

  • A half-brother of one's parent. 

uncle-in-law

noun

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

  • The uncle of one's wife. 

  • The uncle of one's husband. 

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