firkin vs milker

firkin

noun
  • A small wooden vessel or cask of indeterminate size, used for butter, lard, etc. 

  • A varying measure of capacity, usually being a quarter of a barrel; specifically, a measure equal to nine imperial gallons. 

  • A weight measure for butter, equalling 56 pounds. 

milker

noun
  • A milking machine. 

  • A woman’s breast. 

  • A person who milks. 

  • An animal, such as a dairy cow, kept for the milk it produces. 

  • A conservative poker player who only raises the stakes on a good hand. 

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