fettler vs oppo

fettler

noun
  • A friend or mate 

  • A person who maintains railway lines. 

  • Someone who fiddles or tinkers with things. 

  • An ostler; one who looks after the horses in a mine. 

  • Someone whose job is to sand and grind small imperfections from metal and ceramic castings. 

oppo

noun
  • A friend, associate or colleague. 

  • Research into one's opponent's family, friends, and past, which aims to uncover activities or interests which embarrass or discredit them. 

How often have the words fettler and oppo occurred in a corpus of books? (source: Google Ngram Viewer )