casket vs treasure chest

casket

noun
  • A little box, e.g. for jewellery. 

  • A gasket. 

  • An urn. 

  • A coffin. 

verb
  • To put into, or preserve in, a casket. 

treasure chest

noun
  • A chest filled with treasure, especially one used by pirates, etc. 

  • Any source of something valuable or beautiful. 

  • A treasury, especially a state or royal treasury. 

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