pony keg vs soda fountain

pony keg

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

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

soda fountain

noun
  • An apparatus for dispensing carbonated soft drinks. 

  • A counter, in a shop, at which sodas, ice-creams etc are prepared and served. 

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