death march vs threnody

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. 

threnody

noun
  • A song or poem of lamentation or mourning for a dead person; a dirge; an elegy. 

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