on the level vs upon the square

on the level

prep

  • Synonym of on the square (“discreet reference to freemasonry”) 

  • Honest(ly), sincere(ly), straightforward(ly), fair(ly). 

upon the square

prep

  • Synonym of on the square 

How often have the words on the level and upon the square occurred in a corpus of books? (source: Google Ngram Viewer )