memorial service vs threnode

memorial service

noun
  • A ceremony to honor a deceased person; a funeral. 

  • An informal service honoring a deceased person, especially one that does not adhere to the traditional customs of a funeral. 

threnode

noun
  • A threne, or threnody; a dirge; a funeral song. 

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