packing case vs pail

packing case

noun
  • A large, sturdy box or wooden crate used for the secure shipment of goods. 

pail

noun
  • A closed (covered) cylindrical shipping container. 

  • A vessel of wood, tin, plastic, etc., usually cylindrical and having a handle -- used especially for carrying liquids, for example water or milk; a bucket (sometimes with a cover). 

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