allowable vs fit for purpose

allowable

adj
  • Appropriate; satisfactory; acceptable. 

  • Intellectually admissible; valid; probable. 

  • Able to be added or deducted in consideration of something. 

  • Permissible; tolerable; legitimate. 

noun
  • permitted amount or activity. 

fit for purpose

adj
  • appropriate, and of a necessary standard, for its intended use. 

How often have the words allowable and fit for purpose occurred in a corpus of books? (source: Google Ngram Viewer )