chain store vs pony keg

chain store

noun
  • A retail outlet that is one of a group of similar establishments having common format, contents, ownership and management. 

pony keg

noun
  • A drive-through liquor store; by extension, any convenience store. 

  • A container for beer holding 7.75 US gallons, equal to half the size of a standard beer keg. 

How often have the words chain store and pony keg occurred in a corpus of books? (source: Google Ngram Viewer )