arduity vs throe

arduity

noun
  • The state or quality of being arduous; steepness, difficulty. 

throe

noun
  • A hard struggle, especially one associated with the beginning or finishing of a task. 

  • Any severe pang or spasm, especially an outburst of feeling; a paroxysm. 

  • The pain of labour or childbirth; the suffering of death. 

  • Synonym of froe (“a cleaving tool for splitting cask staves and shingles from a block of wood”) 

  • A severe pang or spasm of pain, especially one experienced when the uterus contracts during childbirth, or when a person is about to die. 

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