firkin vs hogshead

firkin

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

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

  • A weight measure for butter, equalling 56 pounds. 

hogshead

noun
  • An English measure of capacity for liquids, containing 63 wine gallons, or about 52+¹⁄₂ imperial gallons; a half pipe. 

  • A large barrel or cask of indefinite contents, especially one containing from 100 to 140 gallons. 

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