bread and butter vs retainment

bread and butter

intj
  • Said when two people walking together are temporarily separated by an obstacle in order to indicate that they belong together. 

noun
  • That which is central or fundamental, as to one's business, survival, or income; a staple or cornerstone. 

  • Used other than figuratively or idiomatically: see bread, butter. 

retainment

noun
  • retention 

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