carriage trade vs main line

carriage trade

noun
  • Retail business with wealthy or upper-class customers, i.e. those who arrive in carriages 

  • Wealthy or upper-class people in general 

main line

noun
  • A standard sequence of opening moves considered to be best play. 

How often have the words carriage trade and main line occurred in a corpus of books? (source: Google Ngram Viewer )