cutting edge vs spearhead

cutting edge

noun
  • The sharp edge of the blade of a knife or other cutting tool. 

  • The forefront, or position of greatest advancement in some field. 

spearhead

noun
  • The pointed head, or end, of a spear. 

  • The leading military unit in an attack. 

  • One who leads or initiates an activity (such as an attack or a campaign). 

  • A player who initiates attacking moves. 

verb
  • To drive or campaign ardently for, as an effort, project, etc. 

How often have the words cutting edge and spearhead occurred in a corpus of books? (source: Google Ngram Viewer )