oner vs round peg in a square hole

oner

noun
  • A small marble of little worth in children's games. 

  • A long one-take shot, or equivalent animated segment simulating a one-take shot 

  • An extraordinary individual. 

  • A conker that has won one match. 

round peg in a square hole

How often have the words oner and round peg in a square hole occurred in a corpus of books? (source: Google Ngram Viewer )