package store vs pony keg

package store

noun
  • A retail liquor store, specifically one in which only sealed containers may be sold for consumption off the premises. 

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 package store and pony keg occurred in a corpus of books? (source: Google Ngram Viewer )