death march vs elegy

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. 

elegy

noun
  • A mournful or plaintive poem; a funeral song; a poem of lamentation. 

  • A composition of mournful character. 

  • A classical poem written in elegiac meter 

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