death march vs threnode

death march

noun
  • Synonym of dead march (“mournful music for a funeral etc.”) 

  • A forced movement of people, on foot, in such circumstances that many die during the journey. 

  • A project that requires a stretch of unsustainable overwork, or whose participants feel it is destined to fail. 

threnode

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

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